Chewy Turtle Cake
["3 Tbsp. boiling water", "2 oz. sweet cooking chocolate", "3/4 c. sugar", "1/4 c. + 2 Tbsp. margarine, softened", "2 egg yolks", "1/2 tsp. vanilla", "1 c. cake flour", "1/2 tsp. baking soda", "1/4 tsp. salt", "1/4 c. + 2 Tbsp. buttermilk", "2 egg whites"]
["Pour boiling water on chocolate.", "Melt and cool.", "Grease and flour rectangle pan, 13 x 9-inch.", "Beat sugar and margarine until fluffy.", "Beat in egg yolks, one at a time.", "Beat in chocolate and vanilla on low speed.", "Mix in flour, baking soda and salt, alternating with buttermilk, beating after each addition until batter is smooth.", "Beat egg whites until stiff.", "Fold into batter; pour in pan.", "Bake for 20 minutes in 350\u00b0 oven.", "Spread Caramel Topping over cake.", "Top with chocolate chips and nuts.", "Bake about 20 minutes or until chips are melted."]
["boiling water", "sweet cooking chocolate", "sugar", "+", "egg yolks", "vanilla", "cake flour", "baking soda", "salt", "+", "egg whites"]