We did not fill our cupcakes, but we often do! If you would like to add more whipped cream cheese frosting to the center of the cupcakes, simply add it to a piping bag, snip away the tip, insert it halfway into the unfrosted cupcake, and squeeze for a few seconds. Then frost. It is a good idea to practice on a plate, squeezing the piping bag for a count of a few seconds to get an idea of how much filling will be in your cupcake, and adjust to your liking. (If you have extra strawberry cupcakes, you can do a trial run and then split the cupcake in half to check the amount of filling.) If you plan to use this frosting as a filling, you will likely need to increase the recipe by half.