From: Art of Gluten-Free Baking (http://artofglutenfreebaking.com)
-adapted from Vintage Cakes by Julie Richardson
Yield: 1- 3 layer cake
Ingredients
For the Cake
4 ounces (115 g) unsweetened chocolate, chopped
¼ cup (28 g) unsweetened cocoa
¾ cup (177 ml) boiling water
¾ cup (190 g) sour cream (make sure it is gluten-free)
1 tablespoon vanilla extract
2 cups (290 g) Jeanne’s Gluten-Free All Purpose flour mix
¾ teaspoon baking soda
1 teaspoon salt
½ cup (1 stick; 115 g) unsalted butter, room temperature
1 cup (213 g) packed brown sugar (I like dark brown)
¾ cup (150 g) granulated sugar
½ cup (120 ml) neutral tasting vegetable oil (I like Rice Bran oil)
3 egg yolks at room temperature
3 extra large eggs at room temperature
For the Berry Buttercream
6 extra large egg whites. room temperature
1 ¼ cups granulated sugar
¼ teaspoon cream of tarter
2 cups (4 sticks; 1/2 kg) unsalted butter, at room temperature and cut into cubes
2 teaspoons vanilla extract
1/8 teaspoon salt
4 cups (10 ounces; 283 g) strawberries or raspberries, mashed and strained through a sieve to catch seeds. If using frozen berries, measure before thawing. Discard the seeds
For the Sugar Syrup
¼ cup (50 g) granulated sugar
½ cup (120 ml) boiling water
1 teaspoon vanilla extract
For the Ganache
1 cup (240 ml) heavy cream
1 ¼ cups (227 g) semi-sweet chocolate chips
Make the cake
Preheat oven to 350 degrees F/180 degrees C/Gas Mark 4. Line the bottoms of 3- 8 inch/20 cm round cake pans with parchment paper.
In a medium bowl, pour the boiling water over the unsweetened chocolate and cocoa and let sit for 1 minute. Whisk until smooth. Add the sour cream and vanilla. Whisk well to combine.
Sift together flour, baking soda, and salt in a small bowl.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and both sugars on medium-high until light and fluffy—about 3 minutes. Scrape down the bowl with a rubber spatula. On low speed, drizzle oil into the mixture until it’s blended. On low speed, add the egg yolks and eggs, one at a time, until well blended. On low speed, add the flour mixture and chocolate mixture alternately, beginning and ending with the flour mixture. Blend until smooth.
Divide the batter equally between the 3 pans (there will be approximately 510 g of batter per pan). Smooth tops and tap each pan on the counter to release and large air bubbles.
Bake at 350 degrees F for about 25 minutes—until the centers of the cakes spring back when lightly touched. Place pans on wire racks to cool for about 10 minutes, then unmold onto wire racks to cool completely.
When the cakes are completely cool, wrap each tightly in a piece of plastic wrap and place in the freezer for at least an hour or overnight.
Make the ganache
Heat the cream at very low temperature until bubbles form around the edges. Immediately remove from heat and add the chocolate chips. Let stand for 1 minute and then whisk until smooth. As you make the buttercream, the ganache will start to cool and set up. You want it to be stiff enough to spread like a frosting rather than pour like a glaze.
Make the Berry Buttercream
When you are ready to frost your cakes, prepare your buttercream. This will make a what is called a Swiss Buttercream—which means that the egg whites are cooked as they are beaten with the sugar and cream of tartar over simmering water.
In the bowl of a stand mixer, place egg whites, sugar, and cream of tartar. Use a hand whisk to combine. Place bowl over (not in) a pan of simmering (not boiling) water and whisk constantly. As the mixture warms up, it will become easier to whisk. Continue whisking until the side of the bowl is hot to the touch.
Carefully move the bowl to the stand mixture and using the whisk attachment, whip the whites on medium high until they have tripled in volume and are glossy and they hold stiff peaks, 3-4 minutes. Turn the speed to low and add butter pieces, one at a time. Add each piece after the piece before it has been incorporated into the mixture. The mixture may go through a phase where it looks curdled—that’s OK, it is normal and will eventually smooth out. Once all of the butter is incorporated and the frosting looks smooth, add the mashed and strained berries, vanilla, and salt until combined.
You can now cover with plastic wrap and make your ganache. If you’re not using it fairly soon, the buttercream will keep at room temperature for about 2 days or in the fridge for about 7 days. If you place it in the fridge, you will need to bring it to room temperature. Either way, the buttercream must be re-whipped, either by hand or in the bowl of a stand mixer fitted with the whisk attachment.
Make the sugar syrup
Combine the boiling water, sugar, and vanilla in a small pan. Stir until sugar has completely dissolved. Let cool to lukewarm before using on the cake layers.
Frost and assemble the cake
Remove the first layer from the freezer and unwrap. Place bottom side up on the cake plate (the bottoms are usually flatter than the tops).
Tip: to save on clean up time, place cut pieces of waxed or parchment paper around the edges of the bottom cake layer—shoving them under the cake. This way, the paper catches frosting/ganache drips. Then when you’re done frosting the cake, remove the paper pieces—and you have a clean plate!
Using a pastry brush, brush the top with the sugar syrup.
Next, spread a thin layer of the ganache on top.
Next, spread with about ¾ cup of the buttercream. I like to do this with a metal offset spatula. The buttercream will be about ¼ in/.66 cm thick.
Unwrap the next cake layer and stack bottom up on top of the first layer. Repeat the sugar syrup, ganache, and buttercream process.
Unwrap the final cake layer and stack on the top of the second layer. Repeat the sugar syrup and ganache process. Now, check your cake and carefully scrape off any ganache or buttercream that has oozed out of the layers. Then, apply a thin coating of buttercream over the entire cake. You should be able to see parts of the cake through the buttercream. This is your “crumb coat.” What this does is contain any loose crumbs that are present on the cake so they don’t get mixed up into your final frosting and make it look messy.
Place the cake into the refrigerator for about 10 minutes to firm up the crumb coat before you do your final frosting. After 10 minutes, remove from fridge and carefully frost the cake with the remaining buttercream.
Store the cake in an airtight container (I like to use a cake carrier) for up to 3 days.