For the cupcakes, beat butter and sugar until creamy. Add in eggs beating after each addition.
In a separate bowl, stir together flour and baking powder. Gradually alternate adding flour mixture and milk to the sugar mixture, while beating, until ingredients are well combined.
Divide evenly among 24 paper lined muffin cups. Bake at 350 for 15 - 17 minutes or until a cake tester comes out clean. Cool completely.
To prepare the frosting, beat butter, powdered sugar, and milk until light and fluffy.
Using a small knife, cut a small hole into the center of each cupcake. Fill with small treats. Frost and decorate as desired.