Grandma'S Marble Cake
["1 c. butter", "2 c. sugar", "4 eggs, separated", "1 c. milk", "1/8 tsp. salt", "3 1/4 c. sifted flour", "3 tsp. baking powder", "1 tsp. vanilla", "2 sq. Baker's chocolate, melted in 2 1/2 Tbsp. hot water"]
["Grease 9 x 13-inch pan (do not flour).", "Cream butter and sugar together.", "Add egg yolks, beaten well.", "Sift salt, baking powder and flour.", "Add to first mixture, alternating with milk.", "Add vanilla and beat well.", "Divide batter into 2 parts.", "Add chocolate to one.", "Beat egg whites until stiff.", "Divide it in half, fold each half into each half of batter (1/2 in chocolate and 1/2 in vanilla).", "Put one spoonful of vanilla and one of chocolate alternating until you fill the pan.", "Bake at 350\u00b0 until done (approximately 45 minutes)."]
["butter", "sugar", "eggs", "milk", "salt", "flour", "baking powder", "vanilla", "chocolate"]