1 c. boiling water
3 oz. unsweetened chocolate
8 tbsp. (1 stick) sweet butter
1 tsp. vanilla extract
2 c. granulated sugar
2 eggs, separated
1 tsp. baking soda
1/2 c. dairy sour cream
2 c. less 2 tbsp. sifted unbleached all-purpose flour
1 tsp. baking powder
Chocolate Frosting (recipe below)

1. Preheat oven to 350 degrees. Grease and flour 10 inch tube pan. Knock out excess flour.

2. Pour boiling water over chocolate and butter; let stand until melted. Stir in vanilla and sugar. Whisk in egg yolks, one at a time, blending well after each addition.

3. Mix baking soda and sour cream. Whisk into chocolate mixture.

4. Sift flour and baking powder together; add to batter, mixing thoroughly.

5. Beat egg whites until stiff but not dry. Stiff a quarter of the egg whites into the batter thoroughly. Scoop remaining egg whites on top of batter and gently fold together.

6. Pour batter into prepared pan. Set on the middle rack of the oven and bake 40-50 minutes, or until the edges have pulled away from the sides of the pan and a cake tester inserted into the center comes out clean. Cool in pan for 10 minutes; unmold and cool completely before frosting.

CHOCOLATE FROSTING:

2 tbsp. sweet butter
3/4 c. semi-sweet chocolate chips
1 tsp. vanilla extract
6 tbsp. heavy cream
1-1 1/4 c. sifted confectioners' sugar or as needed

Place all ingredients in a heavy saucepan over low heat and whisk until smooth. Cool slightly; add more sugar if necessary to achieve a spreading consistency. Spread on cake while frosting is still warm.