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.

Preheat oven to 350F. To prepare cake, combine boiling water and cocoa powder in a bowl, stirring until smooth. Add chocolate; stir until smooth. Set aside to cool to room temperature. Meanwhile, coat two 8-inch round cake pans with baking spray or butter.,______,In a separate bowl, combine flour, cornstarch, baking powder, baking soda and salt. Stir to mix. Add flour mixture and cocoa mixture alternatively to sugar mixture, beginning and ending with flour mixture and beating until just combined. Divide batter evenly between the 2 prepared pans. Bake at 350F for 25 minutes or until a wooden toothpick comes out with just a few crumbs. Cool in pans 10 minutes, then place on wire racks to cool completely.,To make the filling, combine Cool Whip, orange zest and juice in a bowl. Set aside to assemble cake.,To make the chocolate glaze, combine evaporated milk, butter and chocolate in a microwave safe bowl. Microwave for 1 minute, stirring every 15 to 20 seconds until smooth.,Place cake layer on a plate and top with orange filling. Place the other cake on top and spoon chocolate glaze on top until it's just falling over the edges.
Place the sugar, butter and vanilla in a large bowl. Beat with a mixer at medium speed 1 minute. Add egg whites, one at a time, beating well after each addition. Add sour cream; beat at medium speed 2 minutes. Egg whites should become slightly fluffy.