Prepare cake mix as directed. Stir in espresso powder and bake according to the package directions.

Cool completely on a wire rack before frosting.

On medium-high speed, beat together the shortening and butter until fluffy.

In a small bowl, mix together the vanilla, milk and espresso powder, stirring until the powder is completely dissolved.

On medium speed, slowly add the vanilla mixture to the butter mixture. When combined, gradually add the sugar, continue mixing until light and fluffy.