Marble Chiffon Cake

2 (1 ounce) squares chocolate
1/4 cup hot water
1/4 cup granulated sugar
1/4 teaspoon baking soda
2 cups sifted all-purpose flour
1 1/2 cups sugar
3 teaspoons baking powder
Pinch of salt
7 unbeaten egg yolks
1/2 cup vegetable oil
3/4 cup water
2 teaspoons vanilla extract
1 cup egg whites (7)
1/2 teaspoon cream of tartar

Melt chocolate. Add hot water, sugar and baking soda; mix well.

In first bowl sift together flour, sugar, baking powder and pinch of salt. Form a well. Add egg yolks, oil, water and vanilla extract. Beat until smooth.

In second bowl put egg whites and cream of tartar. Beat until stiff. Pour batter over egg whites. Divide batter in half and add chocolate mixture to half. Spoon into ungreased tube pan. Swirl to marbleize.

Bake at 350 degrees F for 10 minutes then at 325 degrees F for 55 minutes.

Frosting:
1/4 to 1/2 cup water
1 heaping cup brown sugar
Pinch of salt
1 tablespoon butter
1 teaspoon vanilla extract
Confectioners' sugar

Combine water, brown sugar and salt. Bring to a rolling boil. Remove from heat. Add butter and vanilla extract. Thicken with confectioners' sugar (not too thick). Can flavor with chocolate or cocoa, if desired.