Makes about 9 cups, enough for about 28 cupcakes
2 1/2 cups sugar
10 large egg whites
4 cups (8 sticks or 2 pounds) unsalted butter, cut into pieces
2 teaspoons pure vanilla extract
Place sugar and egg whites in the heat-proof bowl of an electric mixer. Set bowl over a pan of gently simmering water, and whisk until sugar has dissolved and egg whites are hot to the touch, about 3 minutes. Test by rubbing the mixture between your fingers; it should feel completely smooth.
Transfer bowl to mixer stand. Using the whisk attachment, beat on high speed until mixture has cooled completely and formed stiff and glossy peaks, about 10 minutes.
Add the butter, one piece at a time, and beat until incorporated after each addition. Don't worry if the buttercream appears curdled after all the butter has been added; it will become smooth again with continued beating. Add vanilla, and beat just until combined.
Switch to the paddle attachment, and beat on the lowest speed to eliminate any air pockets, about 5 minutes. If using buttercream within several hours, cover bowl with plastic wrap, and set aside at room temperature in a cool environment. Or transfer to an airtight container, and store in the refrigerator, up to 3 days. Before using, bring buttercream to room temperature, and beat on the lowest speed with the paddle attachment until smooth, about 5 minutes.
Prep: 30 minutes
Total: 1 hour Makes 12
3/4 cup unsweetened cocoa powder
3/4 cup all-purpose flour
1/2 teaspoon baking powder
1/4 teaspoon salt
3/4 cup (1 1/2 sticks) unsalted butter, room temperature
1 cup sugar
3 large eggs
1 teaspoon vanilla extract
1/2 cup sour cream
Easy White Icing
Sprinkles (optional)
Preheat oven to 350 degrees. Line 12-cup standard muffin tin with paper liners.
Into a medium bowl, sift together cocoa, flour, baking powder, and salt; set aside. In a mixing bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each, then beat in vanilla. With mixer on low speed, add flour mixture in two batches, alternating with sour cream and beginning and ending with flour.
Pour batter into cups, filling each 3/4 full. Bake until a toothpick inserted in centers comes out clean, 20 to 25 minutes.
Cool in pan 5 minutes; transfer to a wire rack to cool completely, then spread with Easy White Icing using a table knife or small offset spatula. Decorate with sprinkles, if desired.