01 - Beat the softened butter in a medium bowl until creamy and smooth.
02 - Gradually mix in the sifted powdered sugar on low speed until combined.
03 - Add heavy cream and peppermint extract, then beat on medium speed until smooth and fluffy, about 2 minutes.
04 - If desired, blend in green food coloring until evenly tinted.
05 - Use immediately for fillings or refrigerate in an airtight container up to one week.