Turtle Cake
["1 box German sweet chocolate cake mix", "1 (14 oz.) pkg. vanilla custard", "3/4 c. margarine", "1/2 c. evaporated milk", "1/2 to 3/4 c. chocolate chips", "1 c. chopped walnuts or other nuts"]
["Mix cake as directed on package.", "Grease a 9 x 13 x 2-inch pan.", "Pour half batter in pan and bake at 350\u00b0 for 15 minutes."]
["sweet chocolate cake", "vanilla custard", "margarine", "milk", "chocolate chips", "walnuts"]