German Sweet Chocolate Cake
["1 bar (4 oz.) Baker's German sweet chocolate", "1/2 c. boiling water", "2 c. sugar", "1 tsp. vanilla", "2 1/2 c. sifted flour", "4 egg yolks, unbeaten", "4 egg whites, stiffly beaten", "1 tsp. baking soda", "1/2 tsp. salt", "1 c. buttermilk"]
["Melt chocolate in boiling water.", "Cool.", "Cream margarine and sugar until fluffy.", "Add egg yolks one at a time beating well after each one.", "Add melted chocolate and vanilla.", "Mix well. Sift together flour, salt and baking soda.", "Add alternately with buttermilk to the chocolate mixture.", "Beat well each time.", "Beat until smooth.", "Fold in egg whites.", "Pour into 3 deep 8 or 9-inch cake pans, lined on bottom with wax paper.", "Bake at 350\u00b0 for 30 to 40 minutes.", "Cool.", "Frost tops only."]
["sweet chocolate", "boiling water", "sugar", "vanilla", "flour", "egg yolks", "egg whites", "baking soda", "salt", "buttermilk"]