3 squares baking chocolate
5 tbsp. hot water
1/2 c. butter
1 1/2 c. sugar
4 eggs, separated
1 3/4 c. sifted cake flour
2 tsp. baking powder
1/2 tsp. salt
1/2 c. milk
1 tsp. vanilla

Melt baking chocolate, cut into small pieces with hot water in top of double boiler. Cream butter and sugar together. Add egg yolks, well beaten and whip thoroughly. Add melted chocolate mixture, slightly cooled, flour sifted with baking powder and salt and the milk. Fold in whipped egg whites and vanilla. Pour into well greased and floured pan (13"x9"x2"). Bake in moderate oven, 350 degrees, 40 to 45 minutes or until done.