This is a delicious, easy make-ahead dessert which serves 18. Begin the chocolate topping first:

1 c. sugar
1/3 c. cocoa
1/4 c. milk

Heat these in a small saucepan just until the sugar is dissolved well and then add 1 teaspoon vanilla and 1/2 stick butter. Stir well and do not remove from heat however, do not let boil.