01 - Place Fruity Pebbles cereal in a food processor or a zip-top bag. Pulse or crush with a rolling pin until finely ground. Set aside.
02 - In a large mixing bowl, beat the softened butter with an electric mixer on medium speed until creamy and smooth, about 1 to 2 minutes.
03 - Add the powdered sugar, 1/2 cup at a time, beating well after each addition. Scrape down the sides of the bowl as needed to ensure even mixing.
04 - Add the ground Fruity Pebbles, vanilla extract, salt, and milk. Beat on medium-high speed until the frosting is light and fluffy, approximately 2 minutes.
05 - Check the frosting texture. Add more milk, 1/2 tablespoon at a time, for a thinner spread, or additional powdered sugar for a stiffer consistency.
06 - Spread or pipe the frosting onto cooled cakes, cupcakes, or cookies. Garnish with whole Fruity Pebbles just before serving to preserve their crunch.