6 eggs
1 c. butter
2 c. sugar
1 c. brown sugar
1/2 c. cocoa
2 1/2 c. all-purpose flour
1/4 tsp. baking soda
1 c. sour cream
1 tsp. vanilla

Preheat oven to 350°F.

Bake 1 hour and 30 minutes.

Separate eggs; beat whites until stiff and set aside. Soften butter; add sugar, brown sugar and egg yolks. Mix flour with cocoa. Add baking soda, sugar, butter and egg mixture, sour cream and vanilla. Mix to blend. Fold in egg whites.