You will be given a definition of a task first, then some input of the task.
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.

Sift together flour, sugar, and salt.,Set aside.,In saucepan, melt butter, water, shortening and cocoa.,Bring to a boil and pour over flour mixture.,Stir well.,In another bowl, dissolve soda in buttermilk.,Add eggs and vanilla.,Mix well and add to rest of mixture.,Bake in 15 x 10 pan at 350° for 20 minutes.,______
Output:
Frost when cool.