1/2 c. unsweetened cocoa
1/2 c. boiling water
1/4 c. butter, softened
1/4 c. shortening
2 c. sugar
1/8 tsp. salt
1 tsp. vanilla
2 eggs
1 1/2 tsp. baking soda
1 c. buttermilk or sour milk
1 3/4 c. unsifted all-purpose flour
3 tbsp. buttermilk or sour milk
1/8 tsp. baking soda
3/4 tsp. grated orange peel
1/4 tsp. orange extract
Orange Buttercream Frosting (below)

To sour milk: Use 1 tablespoon vinegar plus milk to equal 1 cup; use 1/2 teaspoon vinegar plus milk to equal 3 tablespoons.

Grease 3 (8 or 9-inch) layer pans and line with wax paper; set aside. Stir together cocoa and boiling water until smooth; set aside. Cream butter, shortening, sugar, salt and vanilla in large mixer bowl until light and fluffy. Add eggs; beat well. Stir 1 1/2 teaspoons baking soda into 1 cup buttermilk or sour milk; add alternately with flour to creamed mixture.

Measure 1 2/3 cups batter into small bowl. Stir in 3 tablespoons buttermilk or sour milk, 1/8 teaspoon baking soda, the orange peel and orange extract; pour into 1 prepared pan. Blend cocoa mixture into remaining batter; divide evenly among remaining 2 prepared pans. Bake at 350 degrees for 25 to 30 minutes or until cake tester comes out clean. Cool 10 minutes; remove from pans. Cool completely.

Place one chocolate layer on serving plate, spread with some of the Orange Buttercream Frosting. Top with orange layer and spread with frosting. Top with remaining chocolate layer and frost entire cake. 10 to 12 servings.

ORANGE BUTTERCREAM FROSTING:

2/3 c. butter, softened
6 c. confectioners' sugar
2 tsp. grated orange peel
1 1/2 tsp. vanilla
4 to 6 tbsp. milk

Cream butter, 1 cup confectioners' sugar, the orange peel and vanilla in large mixer bowl. Add remaining confectioners' sugar alternately with milk, beating to spreading consistency.