3 egg yolks
1 cup sour cream
1 1/2 cups sugar
2 (1 oz) squares unsweetened chocolate
1/4 cup hot water
1 tsp. vanilla
1 3/4 cups cake flour
1/2 tsp. baking soda
3 egg whites

Preheat oven to 350°F. Grease two 8 inch round pans or 1 loaf pan.

Beat the egg yolks with sour cream; add sugar gradually and beat until thick. Melt chocolate in hot water, add to first mixture with vanilla. Add the sifted dry ingredients. Using a clean beater and mixing bowl, beat the egg whites until they hold stiff peaks. Fold the egg whites gently into the batter.

Spread batter thinly and evenly in prepared round cake pans (about 1/2 inch thick) or fill loaf pan.

Bake for about 45-50 minutes or until a toothpick inserted in center of cake comes out clean. Loaf pan may take 5-10 minutes longer to bake.

Note: Do not open oven to test cake until at least 40 minutes have passed or the cake may fall. Once a cake falls, it will never finish baking! Not recommended for toaster ovens.