2 1/2 cups unsifted flour
1/2 cup unsweetened cocoa
1/2 teaspoon baking powder
1/4 teaspoon baking soda
2 cups granulated sugar
1 cup firmly packed light brown sugar
3/4 cup butter, softened
6 eggs, separated
1 teaspoon vanilla extract
8 ounces sour cream

Preheat oven to 325 degrees F.

Stir together flour, cocoa, baking powder and baking soda; set aside.

In large mixer bowl, combine sugars and butter; beat until light and fluffy. Add egg yolks, one at time, beating well after each addition; add vanilla extract. Beat in sour cream alternately with dry ingredients (batter is very thick).

In medium bowl, beat egg whites until stiff but not dry; fold half into batter. Fold in remaining egg whites. Pour into well-greased and floured 10-inch tube or fluted pan. Bake 1 1/2 hours or until wooden pick inserted in center comes out clean. Cool 10 minutes; remove from pan. Sprinkle with confectioners' sugar, if desired.

Makes one 10-inch cake.