This frosting is delicious. I tried to make pina colada cupcakes as well but they did not turn out so well. I will have to work on the recipe some more. I also topped the cup cake with toasted coconut.
1 Stick (8 Tbs.) butter, softened
1/2 cup vegetable shortening
1 tsp. rum extract
2 tsp. coconut extract
2 1/2 Tbs. pineapple juice
4 cups powdered sugar
1-2 Tbs. milk
Beat butter and shortening with electric mixer until blended. Beat in extracts and juice, add sugar and beat until blended. Add milk until frosting is the consistency that you would like.