German Sweet Chocolate Cake
["1 (4 oz.) pkg. Baker's German's sweet chocolate", "1/2 c. boiling water", "2 c. sugar", "2 1/4 c. plain flour", "1 tsp. soda", "1/2 tsp. salt", "1 c. buttermilk", "4 egg yolks", "1 tsp. vanilla", "1 c. butter", "4 egg whites, beaten"]
["Melt chocolate in boiling water. Cool. Cream butter and sugar. Add egg yolks, beating well after each. Blend in vanilla and chocolate. Sift flour with soda and salt; add alternately with buttermilk to chocolate mixture. Mix well. Fold in beaten egg whites. Bake in 4 (9-inch) pans at 325\u00b0 for 30 minutes."]
["chocolate", "boiling water", "sugar", "flour", "soda", "salt", "buttermilk", "egg yolks", "vanilla", "butter", "egg whites"]