- 1 2/3 cups cake flour
- 1/2 cup unsweetened cocoa powder
- 1 tablespoon baking powder
- 1/2 teaspoon salt
- 1 1/3 cups plus 3/4 cup sugar
- 1/2 cup (1 stick) unsalted butter, room temperature
- 3 large eggs, separated
- 1 large egg
- 1 cup buttermilk
- 1 cup miniature semisweet chocolate chips (about 6 ounces)
- Preheat oven to 325°F. Generously butter 9-inch-diameter springform pan with 2 3/4-inch-high sides; dust with flour. Sift first 4 ingredients into small bowl. Using electric mixer, beat 1 1/3 cups sugar, butter, 3 yolks and 1 whole egg in large bowl until blended. Beat in flour mixture alternately with buttermilk in 3 additions each. Mix in chocolate chips.
- Using clean dry beaters, beat 3 egg whites in medium bowl until soft peaks form. Gradually add 3/4 cup sugar, beating until stiff glossy peaks form, about 5 minutes. Spread 2/3 of meringue halfway up sides (not on bottom) of prepared pan. Spoon batter into meringue-lined pan; top with remaining meringue. Using tip of knife, swirl top meringue and some of chocolate batter together.
- Bake cake until tester inserted into center comes out with a few crumbs attached, about 1 hour 15 minutes. Cool 10 minutes on rack. Cut around pan sides; release pan sides. Cool completely.