Preheat oven to 350 degrees. Roll sprinkles into cookie dough. Roll out 1 oz balls of cookie dough into a Sweet Creations Textured 24-Cup Nonstick Mini Muffin/Cupcake Pan. Bake for 10 minutes and then remove from oven.
While still hot, carefully press down centers of cookies with a small fondant rolling pin.
For the frosting, place butter in a medium bowl with an electric mixer and beat until creamy. Beat in vanilla. Sprinkle in powdered sugar, 1/2 cup at a time, beating well and scraping sides of bowl often. Add milk, 1 tsp at a time until desired consistency is reached.
Once cookies have cooled, using a piping bag and a medium-sized piping tip to fill pressed divots with frosting and top with sprinkles.