Given the task definition and input, reply with output. In this task, you will be presented with the directions of a recipe separated by "," and have to fill in the "___" which is a step that is missing from the recipe.

Cake: Mix flour and sugar,,Heat margarine, cocoa, oil and water until boiling,,Pour hot mixture over flour and sugar and mix well,,Add butttermilk, baking soda, eggs and vanilla,,______,,Icing: Mix margarine, cocoa and buttermild - heat until boiling,,Remove from heat and add powdered sugar and vanilla,,Pour over cake while both are hot
Pour into 9x13 pan and bake 30 min at 350 degrees