Saffron Layer Cake with White Chocolate Mousse & Pistachio Buttercream
Hi everyone! Happy New Year!!! Can I tell you something? I had grand plans for a couple of very special posts to say fare well to 2014 and properly greet 2015. But I confess that I zonked out good and well for nearly a week and indulged in some luxurious and sorely needed off-the-grid time off and oh so sweet slumber instead and now I’m off to a family reunion in La La Land (aka the city of angels = Los Angeles) with no time to cobble together a meaningful post. What is a blogger to do? Luckily, I have a glorious ace up my sleeves. A fluffy and decadent guest blog post about a layered cake that is the stuff of dreams. The cake has rosewater, cardamom, pistachio and saffron, which more than qualifies it for the Persianizing round of things and it also has white chocolate mousse and butter cream. Pinch me please! A great way to kick start a food blog’s new year, wouldn’t you say? The recipe and photographs are the handiwork of the impressive culinary talent that is Helen, aka @caramelflahn, whose foodgasmic interview was featured earlier you may recall and whose Instagram account I recommend you all to follow if you’re even a little bit interested in culinary matters of tummy and heart and art. And now without further ado, let’s go read Helen’s delightful ruminations and superb directions on creating a flawless cake.
Saffron Layer Cake with Rosewater-Cardamom White Chocolate Mousse and Pistachio Swiss Meringue Buttercream
A Guest post by Helen of @caramelflahn
One of my absolute favorite flavor combinations is rosewater paired with cardamom and pistachio. It’s impossible for me to pass up anything that has those ingredients together. The delicate yet redolent floral rosewater with the mysterious, almost sultry cardamom is absolutely intoxicating. Throw in the sweet, buttery flavor of pistachios, and you’ve basically described a dream come true to me.
Something else I absolutely love is cake. Baking it, filling it, frosting it, eating it, imagining different flavors and textures of it. Everything. So why not combine cake with rosewater, cardamom, and pistachio? I actually dreamt up this cake in my head years ago and filed it away in my list of “Things That I Think Would Be Good To Make,” but I never got around to creating it until now. Why? I have no idea. Because this is obnoxiously good.
It’s a cottony soft yellow butter cake that I decided to gild the lily with saffron. Because, hey, why not, this is my dream cake, after all. It’s based off of cake guru Rose Levy Beranbaum’s “All-Occasion Yellow Butter Cake”, found in her cookbook classic, The Cake Bible. It has a wonderfully tender, moist crumb that’s delicate, yet holds up well to stacking, filling, and frosting. The yolks make it rich and moist, which is often lacking in white cake, and the butter gives it a delicious flavor. The saffron is steeped in the milk, which is heated ever so slightly to break down the threads. The result is a subtle yet pervasive saffron flavor and lovely golden hue.
The cake layers are split and filled with alternating layers of a creamy rosewater-cardamom white chocolate mousse and a silky pistachio Swiss meringue buttercream, then it’s frosted on the outside with the pistachio buttercream. Seriously? Seriously? Yeah, seriously. Cake is supposed to taste good, so let’s make this taste good! I think white chocolate partners beautifully with rosewater, cardamom, pistachio, and saffron; it’s the element that ties everything together. Since the white chocolate is so rich and rosewater is delicate, I decided to pair them together in a light-textured mousse. The buttercream is a classic Swiss meringue buttercream: super silky with some texture punctuated throughout from the ground pistachios, and not too sweet. I despise the cloyingly sweet and gritty American “buttercream” made with powdered sugar and almost never ever make it. Real buttercream, on the other hand, is an absolute treat to prepare and eat. If you’ve never made it before, it might look a little intimidating, but I guarantee you it’s a snap to make and absolutely worth it.
I hope you enjoy this cake as much as I did!
Saffron Layer Cake with Rosewater-Cardamom White Chocolate Mousse and Pistachio Swiss Meringue Buttercream
Notes for success:
- Please use a good quality white chocolate for the mousse. Those cheap white baking chips will not work. It doesn’t have to be super fancy, just something like Lindt or Ghirardelli will work well.
- The mousse needs to sit in the refrigerator for at least 4 hours, so plan accordingly.
- Cake flour matters. And so does sifting. Please don’t try to substitute with all-purpose flour, or your cake will come out heavy and coarse.
Rosewater-Cardamom White Chocolate Mousse
1 tablespoon rosewater (I like Cortas brand the best)
2 tablespoons water
¾ teaspoon unflavored gelatin
6 ounces good quality white chocolate, such as Lindt, very finely chopped
1 tablespoon granulated sugar
2 large egg yolks
1 ½ cups heavy cream, divided
2 or 3 green cardamom pods, seeds only, finely ground (or rounded ¼ teaspoon pre-ground cardamom)
Saffron Cake (barely adapted from Rose Levy Beranbaum’s The Cake Bible)
1 cup whole milk
2 large pinches of saffron, crumbled
6 large egg yolks
2 ¼ teaspoons vanilla extract
3 cups (300g) sifted cake flour
1 ½ cups (150g) granulated sugar
1 tablespoon + 1 teaspoon baking powder
¾ teaspoon salt
12 tablespoons (1 ½ sticks) unsalted butter (must be softened)
Pistachio Swiss Meringue Buttercream
8 large egg whites
1 ¼ cups granulated sugar
2 ½ cups (5 sticks) unsalted butter, very soft but not melted
½ teaspoon cream of tartar
large pinch of salt
2 teaspoons vanilla extract
1 cup shelled, unsalted pistachios, finely ground but not to paste
Combine the rosewater and water in a small bowl. Sprinkle the gelatin on top and let stand for 5 minutes to soften. Set aside.
Place the finely chopped white chocolate in a medium heatproof bowl. In a small bowl, beat the egg yolks with the sugar by hand or with an electric mixer until thick, pale yellow, and a ribbon falls from the whisk or beaters when lifted and slowly disappears back into the yolks in the bowl. (The yolks make the mousse extra rich and silky, and beating them with the sugar to the ribbon stage keeps the yolks from becoming gritty and granular when heat is applied.)
In a small heavy-bottomed pan, bring ½ cup of the heavy cream to a boil. Remove from heat, and temper the beaten yolks by pouring a small amount of the boiled cream into the yolks and whisking constantly. Repeat this process two or three more times, then pour all of the tempered yolks back into the saucepan with the rest of the heated cream. Add the rosewater-gelatin mixture and stir for 30 seconds.
Doing this tempering gradually raises the temperature of the yolks so they won’t get cooked and scrambled by suddenly adding them to the hot cream.
Immediately pour the hot gelatin-yolk-cream mixture into the bowl with the chopped white chocolate. Whisk until smooth and the white chocolate is completely melted. If your white chocolate isn’t chopped fine enough or your cream cooled down too much, you might have to set the bowl over a pot of barely simmering water while whisking to help the white chocolate melt completely.
Place the white chocolate mixture in the refrigerator until thickened, approximately 30 minutes to an hour.
Whip the remaining 1 cup of heavy cream with the cardamom just to stiff peaks. Do not overbeat.Take a dollop of the cardamom whipped cream and beat it as vigorously as you’d like into the thickened chilled white chocolate mixture. This will lighten the white chocolate enough that it will be easy to fold with the rest of the whipped cream.
Once the initial dollop is blended in with the white chocolate mixture, gently and thoroughly fold in the remainder of the cardamom whipped cream, taking care not to deflate the air you whipped into it. There should be no visible streaks of whipped cream. The mousse will look a little too thin and soupy at this point, but it will solidify as it chills.
Cover the bowl and refrigerate until thickened and set, 4 hours. Keep refrigerated until ready to assemble the cake.
Make the cake
In a small heavy-bottomed pan, gently heat the milk and saffron over medium-low heat, gently swirling the pan to help break down the saffron threads. Remove the pan from the heat when the milk is orange-tinged and very warm, but before it starts to scald. Set aside to cool completely. There will be several saffron threads still intact.
Preheat the oven to 350°F. Grease and flour two 9” round cake pans, and line the bottoms with parchment paper. Do this even if your pans are non-stick. You can quickly and easily cut a parchment round by folding a sheet of parchment into 1/16ths, placing the apex at the center of the pan, and cutting away the excess that extends past the edge of the pan.If you would like to use cake strips to prevent the cakes from doming, fasten the moistened strips securely around the sides of the pans. You can also make DIY cake strips by cutting strips of an old bath towel, saturating the strips with cold water, then fastening them around each cake pan with safety pins.
In a medium bowl lightly combine the yolks, 1/4 cup of the cooled saffron milk, and vanilla.
In a large mixing bowl combine the dry ingredients and mix on low speed for 30 seconds to blend. Add the butter and the remaining 3/4 cup saffron milk. Mix on low speed until the dry ingredients are moistened. Increase to medium speed (high speed if using a hand mixer) and beat for 1 1/2 minutes to aerate and develop the cake’s structure. Scrape down the sides. Gradually add the egg mixture in 3 batches, beating for 20 seconds after each addition to incorporate the ingredients and strengthen the structure. Scrape down the sides.
Scrape the batter into the prepared pans and smooth the surface with a spatula. The pans will be about 1/2 full. If you have a scale, you can use it to divide the batter exactly in half. Bake 25 to 35 minutes or until a tester inserted near the center comes out clean and the cake springs back when pressed lightly in the center. The cakes should start to shrink from the sides of the pans only after removal from the oven.
Let the cakes cool in the pan on racks for 10 minutes. Loosen the sides with a small offset metal spatula and invert onto greased wire racks. To prevent splitting, reinvert so that the tops are up and cool completely.
Make the buttercream
Place the egg white and sugar in the bowl of your stand mixer or a large heatproof mixing bowl if using a hand mixer (I highly recommend using a stand mixer if you have one). Set the bowl over a pan of barely simmering water on medium-low heat and whisk by hand until the egg whites and sugar mixture is warm, thin, foamy, and syrupy (120F degrees for those using a thermometer). Make sure the bottom of the bowl isn’t touching the water, or your eggs might get scrambled.
Attach the bowl to your stand mixer fitted with the whisk attachment (or be prepared to get an upper body workout if you’re using a hand mixer). Add the salt and cream of tartar. Beat at medium-high speed until glossy, stiff, but not dry, about 10 minutes. At this point, the meringue should be cooled to room temperature. Feel the sides of the bowl as well as the meringue itself to make sure it’s cooled completely, otherwise the butter will melt when you add it. If the meringue is beaten to stiff peaks but it still feels warm, reduce the speed to low and keep mixing until cooled completely.
Once the meringue is beaten to stiff peaks and cooled completely, scrape down the bowl and gradually add the softened butter on medium-low speed. The meringue will start to deflate as the fat is added, and it most likely will start to break down into an icky curdled, clumpy, lumpy, cottage cheesy-looking hot mess. Fear not! Keep going! That’s just the butter and meringue trying to get acquainted with each other, and it’s normal. Keep the mixer running, and things will eventually come together and smooth out perfectly.
Most meringue buttercream recipes tell you to add the butter a tablespoon or two at a time over medium or medium-high speed, incorporating each pat completely before adding more. I think that’s tedious and not super necessary? I add my butter ⅓ of a stick at a time or a so in quick succession over medium-low speed. Once I see the previous chunk of butter added is mostly smeared in the meringue, I add the next piece until all the butter is added. The butter gets added more quickly this way, there’s a lot less babysitting, and you still get luscious silky smooth buttercream. Also, as an aside, you still get the gross clumpy curdled stage with the standard method, too.
Once the buttercream has come together, scrape the bowl down and give it another quick whir on medium speed. Add the vanilla extract and beat in thoroughly. Scrape the bowl down again. Add the ground pistachios and mix thoroughly. Congratulate yourself on your Swiss meringue buttercream making prowess. The buttercream spreads best and most easily when freshly made at room temperature.
Time to put this bad boy together! Line whatever surface you’ll be keeping the cake on (cake board, platter, cake stand, etc) with strips of parchment paper or wax paper to keep it clean and make your cake look tidy. Fit a pastry bag with a #12 tip and fill it with the pistachio buttercream. Smear a little buttercream in the middle of your cake board/stand/plate/etc to keep the cake from sliding around.
You could do the whole snipped-off Ziploc bag thing, but honestly, a real tip and pastry bag will make your life much easier. I used to do the Ziploc bag thing, and no wonder I hated frosting cakes so much when I did. There’s no structural integrity to the tip, so the buttercream comes out all wonky and wiggly. It’s a mess to fill, and the shape of the bag isn’t very conducive to decorating. A #12 tip costs just $1.50, and you can get a whole box of disposable pastry bags for around $7 at Sur La Table, Jo-Ann, Walmart, and plenty of other places. If you didn’t use cake strips and your layers are domed on top, trim off the dome. Split each cake layer in half with a long bladed serrated knife, cake splitter, or unwaxed dental floss. You will now have 4 layers of equal (more or less) thickness – 2 tops and 2 bottoms. Place a bottom layer cut-side-up onto the smear of buttercream on your cake board or stand; it should be “stuck” now. Pipe a dam of buttercream around the border. Fill with the rosewater-cardamom white chocolate mousse.
Take a top layer and turn it upside down so the cut side is facing up. Place this on top of the mousse-filled bottom tier. Pipe concentric circles of buttercream from the outside-in. Smooth over with an offset spatula.
Take the other top layer and turn it upside down so the cut side is facing up. Place it on top of the buttercream-filled second tier. Pipe a dam of buttercream around the border. Fill with the rosewater-cardamom white chocolate mousse. You will have mousse left over.
Take the final bottom layer and turn upside down so the cut side is facing down. Place it on top of the mousse-filled third tier. Cover the top and sides with a buttercream crumb coat.
Decorate as desired. Refrigerate the cake for about an hour before serving so the buttercream and mousse can firm up a bit before cutting. Run small offset spatula dipped in hot water along the bottom edge of the cake and carefully pull out the parchment or wax paper strips underneath. Let the cake sit at room temperature for 20 minutes or so before serving. For best results, cut the cake with a thin-bladed sharp knife dipped in hot water. Store the cake in the refrigerator and press a piece of plastic wrap against the cut surfaces of the cake to to keep it moist. The buttercream picks up odors very easily, so make sure there isn’t anything strong-smelling in your refrigerator.
A simple smooth-sided frosting with a large offset spatula or a homey rippled frosting would look very pretty. I personally did a petal cake with nothing but a #12 tip and small offset spatula because the wide open #12 tip allowed the bits of pistachio to pass through easily. I initially tried to do a rose cake with a 1M, but it kept clogging from the pistachios. To make a petal cake, simply pipe 5 balls of buttercream straight down the side of the cake. Take your small offset spatula and hold the tip against one ball and parallel to the floor. Swipe the spatula straight across to the right, smearing the buttercream. Repeat with the other 4 balls and continue this pattern around the cake.
Wow, so that was a baking tour de force! Wasn’t it? Thank you dear Helen for this gorgeous and ambitious cake and truly wonderful guest post! I continue to be rendered speechless and somewhat slobbering while considering this cake. And dear readers, there’s one other guest post by Helen which I’m reserving for yet another special occasion and can’t wait to share with you down the road. Meanwhile, what are you doing here? Go get your saffron and cardamom and other ingredients together and let’s go bake this dreamy fluffy mousse buttercream of a cake!