Step 1

Prepare the cake mix as directed and bake in a 9x13 baking dish. Cool.

Step 2

In a large saucepot, combine sugar, milk, shortening, butter, and salt. Bring to a rolling boil over medium-high heat, stirring constantly to prevent scorching.

Step 3

Once it reaches a boil, let it boil for two to three minutes without stirring.

Step 4

Remove from heat and immediately stir in vanilla and cocoa powder. Beat until icing is smooth and starts to lose its shine. Immediately pour it onto the cooled cake. Allow it to cool before serving.