SERVES 10 TO 12
Bring all the ingredients to room temperature before beginning this recipe. Be sure to use cake pans with at least 2-inch-tall sides. This frosting may be made with milk, semisweet, or bittersweet chocolate; we prefer a frosting made with milk chocolate for this recipe. Let the chocolate cool to between 85 and 100 degrees before adding it to the butter mixture. Click here for more information on frosting a layer cake. See the sidebars that follow the recipe.
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CAKE |
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2½ |
cups (10 ounces) cake flour |
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1¼ |
teaspoons baking powder |
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¼ |
teaspoon baking soda |
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¾ |
teaspoon salt |
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1¾ |
cups (12¼ ounces) granulated sugar |
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1 |
cup buttermilk, room temperature |
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10 |
tablespoons unsalted butter, melted and cooled |
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3 |
tablespoons vegetable oil |
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2 |
teaspoons vanilla extract |
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3 |
large eggs, separated, plus 3 large yolks, room temperature |
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Pinch cream of tartar |
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FROSTING |
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20 |
tablespoons (2½ sticks) unsalted butter, softened (68 degrees) |
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1 |
cup (4 ounces) confectioners’ sugar |
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¾ |
cup (2¼ ounces) Dutch-processed cocoa powder |
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Pinch salt |
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¾ |
cup light corn syrup |
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1 |
teaspoon vanilla extract |
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8 |
ounces milk, bittersweet, or semisweet chocolate, melted and cooled |
1. FOR THE CAKE: Adjust oven rack to middle position and heat oven to 350 degrees. Grease two 9-inch round cake pans, line with parchment paper, grease parchment, and flour pans. Whisk flour, baking powder, baking soda, salt, and 1½ cups sugar together in large bowl. In medium bowl, whisk together buttermilk, melted butter, oil, vanilla, and egg yolks.
2. Using stand mixer fitted with whisk, whip egg whites and cream of tartar on medium-low speed until foamy, about 1 minute. Increase speed to medium-high and whip whites to soft billowy mounds, about 1 minute. Gradually add remaining ¼ cup sugar and whip until glossy, stiff peaks form, 2 to 3 minutes. Transfer to bowl and set aside.
3. Add flour mixture to now-empty mixer bowl. With mixer on low speed, gradually pour in butter mixture and mix until almost incorporated (a few streaks of dry flour will remain), about 15 seconds. Scrape down bowl, then beat on medium-low speed until smooth and fully incorporated, 10 to 15 seconds.
4. Using rubber spatula, stir one-third of whites into batter, then add remaining two-thirds of whites and gently fold into batter until no white streaks remain. Divide batter evenly between prepared pans, smooth tops with rubber spatula, and gently tap pans on counter to release air bubbles.
5. Bake until toothpick inserted in center of cake comes out clean, 20 to 22 minutes, rotating pans halfway through baking. Let cakes cool in pans on wire rack for 10 minutes. Remove cakes from pans, discard parchment, and let cool completely, about 2 hours, before frosting. (Cooled cakes can be wrapped tightly in plastic wrap and kept at room temperature for up to 1 day. Wrapped tightly in plastic, then aluminum foil, cakes can be frozen for up to 1 month. Defrost cakes at room temperature before unwrapping and frosting.)
6. FOR THE FROSTING: Process butter, sugar, cocoa, and salt in food processor until smooth, about 30 seconds, scraping down bowl as needed. Add corn syrup and vanilla and process until just combined, 5 to 10 seconds. Scrape down bowl, then add chocolate and process until smooth and creamy, 10 to 15 seconds. (Frosting can be kept at room temperature for up to 3 hours before frosting cake or refrigerated for up to 3 days. If refrigerated, let stand at room temperature for 1 hour before using.)
7. Line edges of cake platter with 4 strips of parchment paper to keep platter clean. Place 1 cake layer on prepared platter. Place about 1½ cups frosting in center of cake layer and, using large spatula, spread in even layer right to edge of cake. Place second cake layer on top, making sure layers are aligned, then frost top in same manner as first layer, this time spreading frosting until slightly over edge. Gather more frosting on tip of spatula and gently spread icing onto side of cake. Smooth frosting by gently running edge of spatula around cake and leveling ridge that forms around top edge, or create billows by pressing back of spoon into frosting and twirling spoon as you lift away. Carefully pull out pieces of parchment from beneath cake before serving. (Assembled cake can be refrigerated for up to 1 day. Bring to room temperature before serving.)