Mix cake according to manufacturer’s instructions. Into a conventional cupcake pan, place paper liners then use a #2 blue scoop to deposit 1.5oz batter into each cavity. Bake at 350F until cupcakes spring back lightly when touched. Let cool completely and depan.
In a mixing bowl, combine 10 pounds Extra-Rich Flavor Buttercreme Style Icing Base, 1 pound 4oz icing shortening, 2 pounds 11.5oz cookie butter, 3oz salt and 24 pounds powdered sugar. Mix with a paddle for 2 minutes on low speed. Add 4 pounds water and scrape down the bowl. Mix for 15-20 minutes on medium speed.
Pipe prepared buttercreme onto cupcakes and garnish with a shortbread cookie. Place prepared cupcakes into white tulip liners if desired.