Classic Birthday Cake
- Vanilla Sponge Cake Layers, baked and cooled
For the syrup:
- 1⁄2 cup water
- 1⁄2 cup granulated sugar
- 2 Tbs. dark rum and 1 Tbs. instant coffee powder, or 1⁄2 tsp. vanilla extract
For the chocolate buttercream:
- 3 egg whites
- 1⁄4 tsp. cream of tartar
- 2⁄3 cup plus 2 Tbs. granulated sugar
- 1⁄4 cup water
- 1 Tbs. light corn syrup
- 20 Tbs. (2 1/2 sticks) unsalted butter, at room temperature, cut into 10 equal pieces
- 1 tsp. vanilla extract
- 8 oz. semisweet chocolate or white chocolate,
chopped and melted
For the chocolate frosting:
- 2 cups confectioners' sugar, sifted
- 16 Tbs. (2 sticks) unsalted butter, at room temperature
- 2 tsp. vanilla extract
- 1 tsp. instant coffee powder (optional)
- 4 oz. unsweetened chocolate, chopped and melted
- 1⁄4 cup heavy cream, at room temperature
In a small saucepan over low heat, combine the water and sugar. Heat, stirring often, until the sugar dissolves and the mixture is hot. Remove from the heat and stir in the rum and coffee or the vanilla extract. Let the syrup cool to room temperature, about 15 minutes.
Make the sugar syrup for the buttercream
In the bowl of a stand mixer or a large mixing bowl, use a whisk to blend the egg whites and cream of tartar until the cream of tartar dissolves, about 1 minute. Set the bowl aside. In a small, heavy-bottomed saucepan, combine the 2⁄3 cup sugar, the water and the corn syrup. Cover the pan, place over low heat and heat until the sugar dissolves, about 5 minutes. Uncover occasionally and stir with a wooden spoon. Increase the heat to high and let the syrup bubble vigorously, without stirring, until it is smooth and thick and registers 240°F on a candy thermometer, about 5 minutes. Use a damp pastry brush to brush down any sugar crystals that form on the sides of the pan. Remove from the heat.
Combine the egg whites and sugar syrup
Fit a stand mixer or handheld mixer with the whip attachment. Beat the egg white mixture with the 2 Tbs. sugar on medium speed until foamy, about 1 minute. Increase the speed to medium-high and continue beating the egg whites until they look white, shiny and smooth and soft peaks form when the whip is lifted, 2 to 3 minutes. Reduce the mixer speed to low and carefully pour the hot syrup in a thin stream in the space between the whip and the sides of the bowl; the bowl will feel hot to the touch. When all of the syrup has been added, increase the mixer speed to medium-low and beat for 5 minutes. At this point, the outside of the bowl will be lukewarm to the touch and the mixture will form stiff peaks when the whip is lifted.
Incorporate the butter for the buttercream
With the mixer on medium-high speed, add the butter to the egg white mixture 1 piece at a time. Beat until each piece is incorporated before adding the next piece. Stop the mixer occasionally and use a rubber spatula to scrape down the sides of the bowl. Add the vanilla extract and the melted chocolate and beat until combined. (If using a handheld mixer, move the beaters around in the bowl to ensure that every bit of the mixture is well beaten.) The buttercream should be soft enough to spread but not pourable. If it is too soft, refrigerate for about 20 minutes to firm it slightly, then, just before using, whisk briefly until smooth.
Make the chocolate frosting
In the bowl of a stand mixer or a large mixing bowl, combine the confectioners' sugar and butter. Fit the stand mixer with the paddle attachment or the handheld mixer with the twin beaters. Beat on low speed until combined, then continue beating until smooth, about 1 minute. Add the vanilla extract and instant coffee and beat on low speed until well mixed. Add the melted chocolate and beat until fully incorporated and the color is uniform. Pour in the cream, increase the mixer speed to medium, and beat until the color lightens and the mixture looks fluffy, about 1 minute. Use the frosting as soon as possible, while it is still soft and spreads easily.
Cut each cake into 2 layers
Place 1 cooled cake on a flat work surface. Hold a ruler alongside it to measure its height and, using toothpicks, mark the midpoint at 4 to 6 equally spaced intervals around the cake. The picks will guide you as you cut the single cake into 2 uniform layers. Using a large serrated knife and a sawing motion, cut the layer in half horizontally to make 2 layers. Place a large sheet of waxed paper on the work surface, lift off the top cake and place, cut side up, on the waxed paper. Place the bottom layer, cut side up, alongside it. Split the remaining cake in the same way and add the layers to the waxed paper, keeping one cut side down (this will be the top of the cake).
Prepare to build the cake
Using a clean pastry brush, brush the top of each of the 4 layers lightly with the cake syrup, using about 3 Tbs. syrup for each layer. The syrup will moisten and add flavor to the cake. Place 4 strips of waxed paper, each cut 2 inches wide, about 1 inch apart on a cake stand or plate. Slide a cake layer, syrup side up, onto the waxed paper strips. The layers are sturdy, but if you are concerned about them cracking, use 2 wide metal spatulas or the removable bottom of a tart pan to help in the transfer.
Fill and frost the cakes
Spoon 1 cup of the chocolate buttercream into a small bowl and set aside. Using an offset spatula, mound about 1 1/4 cups of the buttercream in the center of the cake and evenly spread it to the edges. Position a second cake layer on top of the buttercream, lining up the edges. Spread another 1 1/4 cups buttercream over it in the same manner. Repeat with the bottom half of the remaining cake layer and the remaining buttercream. Position the final layer on top. Using a clean spatula and about 1 cup of the frosting, spread the top and sides of the cake with a thin layer of frosting to seal in the crumbs (this is called a crumb coat). Spoon about half of the remaining frosting in the center of the cake and, using broad strokes, spread it over the top. Holding the spatula nearly perpendicular to the top, spread the remaining frosting over the sides of the cake, turning the plate as needed to frost the sides evenly.
Finish and decorate the cake
Smooth over the top and sides one last time to provide a smooth finish for the decoration. Fit a pastry bag with a small fluted tip, secure it with the coupler, if needed, and fold down the top. Scoop the reserved buttercream into the pastry bag, unfold the bag and twist the top, pressing the buttercream toward the tip. Pipe a shell border on the top and bottom edge of the cake, or pipe dots, rosettes or other decorations.
Serve the cake
Carefully pull out the waxed paper strips from under the cake and discard. Using a large, sharp knife and a light sawing motion, cut the cake into 12 wedges. Or, carefully place on a cake plate with a lid and refrigerate for up to 3 days; bring to room temperature before serving to soften the buttercream and frosting. Makes one 9-inch cake; serves 12.
Pastry Chef's Tip: If you don't own a cake stand, you can improvise by turning the cake pan in which the cake was baked upside down and placing the cake on top of it, to give it added height.
If you are new to piping, practice on a piece of waxed paper before you decorate a frosted cake. You can also experiment with different tips. When you have finished practicing, scrape the frosting back into the pastry bag so none is wasted.
Adapted from Williams-Sonoma Mastering Series, Cakes, Fillings & Frostings, by Elinor Klivans (Simon & Schuster, 2005).