01 - In a large mixing bowl, beat the softened butter with a hand mixer or stand mixer on medium speed until creamy and pale, approximately 2 minutes.
02 - Add the sifted powdered sugar one cup at a time, mixing on low speed after each addition until fully incorporated.
03 - Pour in the whole milk and vanilla extract. Increase speed to medium-high and beat until the frosting is smooth and fluffy, about 2 to 3 minutes.
04 - Using a spatula, gently fold 3/4 cup of Fruity Pebbles cereal into the frosting until evenly distributed throughout.
05 - Spread or pipe the frosting onto completely cooled cupcakes or cakes.
06 - Sprinkle the remaining 1/4 cup of Fruity Pebbles cereal over the frosted desserts just before serving to maintain maximum crunch.