CHOCOLATE SOUR CREAM LAYER CAKE WITH MILK CHOCOLATE BUTTERCREAM
Ingredients
FOR THE CAKE
¾ cup whole milk
3 ounces unsweetened chocolate, chopped
⅓ cup regular sour cream (do not use low-fat or fat-free)
¼ cup unsweetened natural-style cocoa powder
1⅓ cups cake flour, plus additional for dusting (do not use all-purpose flour)
1½ teaspoons baking soda
½ teaspoon salt
8 tablespoons (1 stick) cool unsalted butter, cut into small chunks, plus additional for greasing
1 cup plus 2 tablespoons packed dark brown sugar
2 large eggs plus 1 large egg white, at room temperature
2 teaspoons pure vanilla extract
FOR THE BUTTERCREAM
6 ounces semisweet chocolate, chopped; or semisweet chocolate chips
6 ounces milk chocolate, chopped; or milk chocolate chips
1 cup plus 2 tablespoons confectioners’ sugar
9 tablespoons unsweetened natural-style cocoa powder
24 tablespoons (3 sticks) unsalted butter, at room temperature
3 tablespoons heavy cream
1 teaspoon pure vanilla extract
¼ teaspoon salt
OVEN RACK • center | OVEN TEMPERATURE • 350°F
PREP • Butter and flour the inside of two 8-inch round cake pans.
TO MAKE THE CAKE LAYERS
1 • Warm the milk in a small saucepan set over low heat, just until puffs of steam come off its surface. Meanwhile, melt the unsweetened chocolate in the top half of a double boiler set over about an inch of slowly simmering water or in a bowl in the microwave in 15-second bursts on high, stirring after each.
2 • Whisk the melted chocolate into the warmed milk until smooth; continue to whisk for 1 minute. Then whisk in the sour cream and cocoa powder until smooth. Set aside. Whisk the flour, baking soda, and salt in a medium bowl until uniform. Set aside as well.
3 • Use an electric mixer at medium speed to beat the butter and brown sugar in a large bowl until creamy, smooth, and even light, about 5 minutes, occasionally scraping down the inside of the bowl. Beat in the eggs, one at a time, then beat in the egg white and vanilla extract until smooth.
4 • Turn off the beaters, add the chocolate mixture, and beat at low speed until well incorporated. Turn off the beaters again, scrape down the inside of the bowl, add the flour, and beat at very low speed just until there are no dry specks of flour remaining in the batter. Pour and spread the batter into the prepared pans, dividing it equally.
TO BAKE IT
5 • Bake until firm and set, until a cake tester or toothpick inserted into the center of the rounds comes out clean, about 25 minutes. Cool the cakes in their pans on a wire rack for 10 minutes, then turn them out, remove the pans, and cool upside down to room temperature, about 1½ hours.
TO MAKE THE BUTTERCREAM
6 • Melt the semisweet and milk chocolate in the top half of a double boiler set over about 1 inch of slowly simmering water, stirring often; or melt them in a large bowl in a microwave in 15-second bursts on high, stirring after each. If using a double boiler, scrape the melted chocolate into a large bowl. In any event, set aside to cool for 20 minutes.
7 • Use an electric mixer at medium speed to beat the confectioners’ sugar into the chocolate until smooth and creamy. Beat in the cocoa until well incorporated. Beat in the butter in 1-tablespoon increments, occasionally scraping down the inside of the bowl, until smooth, glossy, and a bit firm. Beat in the cream, vanilla, and salt until smooth.
TO FROST THE CAKE
8 • Lay rectangles of wax paper on a cake plate or stand to protect it. Set one of the cake layers top side up in the center. Dollop on about 1 cup buttercream and smooth it to the layer’s edge, taking care that it doesn’t mound at the center. Set the second layer of cake bottom side up (that is, the flatter side up) on top. Scoop up a little of the buttercream with a spatula and fill in at the edges between the two layers of cake.
9 • Dump the remainder of the buttercream on top of the cake. Using an offset spatula, spread the frosting, letting the excess ooze over the edges. Catch this excess and spread it along the side, taking more off the top as necessary. Gently pull out the sheets of wax paper. Store lightly covered in plastic wrap in the refrigerator for up to 2 days. Let the cake come back to room temperature before serving.
TIP • We tend not to flour cake pans for chocolate cakes since the edges get unsightly as the cake bakes. However, since we’re frosting this cake, we don’t fear the flour! Unsightly edges will be covered up—and the cake layers will slip out of their pans more easily.