In the bowl of a hand or stand mixer fitted with the paddle attachment, combine the 1 cup softened butter and 3 cups confectioners sugar. Starting on low and moving up to medium speed, mix until smooth and creamy.
Turn the mixer off. Mix the 2 tsp water and 1 tsp instant espresso in in a small bowl. Add it to the bowl along with the 1 tsp milk. Mix on low moving up to high speed again and continue mixing until the frosting is smooth and fluffy, about 1 minute.
Frost your cake or cupcakes!
Notes
This recipe makes enough to frost 12 cupcakes or fill and frost 1 9 inch cake with 2 layers. It can be easily doubled!Try it on these Espresso Cupcakes!