President Eisenhower's Favorite Cake

1/2 cup butter
2 cups granulated sugar
3 eggs
1 cup sour milk
2 1/2 cups sifted flour
1 teaspoon baking soda
1 teaspoon baking powder, rounded
2/3 cup cocoa dissolved in 1/2 cup boiling water
1/4 teaspoon salt
1/4 teaspoon vanilla extract

Sift flour, baking soda, baking powder and salt together. Cream shortening; slowly beat in sugar, egg yolks and vanilla extract. Add cocoa and flour mixture alternately with milk. Fold in stiffly beaten egg whites. Pour into 2 greased layer cake tins. Bake 25 minutes at 375 degrees F, or use greased 9-inch square tin, baking 45 minutes at 350 degrees F. Ice with a seven minute frosting.