Slowly drizzle in the heavy cream about 1 tablespoon at a time.
Mix on high to beat air into the buttercream making it fluffy
If you're making more than one color, separate enough frosting into separate containers. Add the colors to the frosting and beat until combined. Frosting should be smooth and fluffly.
Cover any frosting left in the container with a damp paper towel until you're ready to use it. That will keep it from developing a crust.
Notes
Frosting ConsistencyYou want your frosting in a piping consistency. If it's too loose add more powdered sugar. If it's too thick to squeeze through a piping bag, drizzle in additional cream 1 teaspoon at a time.Keep frosting cool. You can put the bag or bowl into the refrigerator if it gets too warm to pipe. Keep it covered in the bowl with a damp paper towel or a lid to keep it from drying out.
This recipe was calculated using the exact brands and measurements I used to make this recipe. If you are following a strict diet please note changing anything will cause the nutritional info to change. My calculations are intended as a guide only.