Preheat oven to 325 degrees. Grease and flour a 10 inch tube or Bundt pan, tapping out any excess flour, and set aside. Cream the butter and Crisco together in a large mixing bowl with an electric mixer till light and fluffy. Add the sugar and continue beating till well blended. Add the eggs one at a time, beating after each addition till well blended. Into another bowl, sift together the flour, baking powder, salt and cocoa and add alternatively with the milk to the batter, beating well. Add the vanilla and beat till well blended. Pour the batter into the prepared pan and "spank" the bottom of the pan to distribute the batter evenly and eliminate any air bubbles. Bake 1 hour and 10 minutes or till a straw or cake tester inserted in the center comes out clean, then let the cake cool completely in the pan before turning out onto a cake plate. With a rubber spatula, spread the frosting liberally and evenly over the top and sides of the cake, let cool completely and keep covered till ready to serve. Makes 12 servings. Chocolate Marshmallow Frosting: In a large, heavy saucepan, combine the sugar, evaporated milk and marshmallows, bring to a boil over moderate heat and cook for 6 minutes, stirring. Remove the pan from the heat, add the butter, chocolate chips and vanilla and beat with a wooden spoon till the frosting is thick and smooth, about 10 minutes. Yields about 3 cups frosting; enough for the top and sides of a 10inch tube cake or a 3layer 9inch cake, or for about 2 dozen cupcakes.