1. Preheat your oven to 350°F. Spray a mini muffin pan with baking spray or nonstick spray.
2. Place one dough square into each muffin cup. Gently press down the center with your thumb to form a small indentation. Smooth the edges to create an even cup shape.
3. Bake for 8-10 minutes or until the edges are golden and set. Don’t worry if the centers puff up—they’ll settle as they cool. If they don’t settle enough, lightly press down into the center with a greased teaspoon. Let them cool in the pan until stable.
4. Once cooled, gently twist each cookie cup out of the pan. Place them on a wire rack to cool completely while you whip up the frosting.
5. In a medium bowl, beat the butter until smooth and creamy.
6. Add powdered sugar, heavy cream, and vanilla until combined. If the frosting is too thick, add more heavy cream one tablespoon at a time.
7. Fill a piping bag fitted with a 1M tip and pipe a swirl of frosting into each cookie cup.
8. Alternatively, add a dollop of frosting and smooth it out with a knife. FYI: You’ll use less frosting this way and have some left over!
9. Top each frosted cookie cup with rainbow sprinkles. Be as generous as you’d like!