Add champagne to a small saucepan and heat until it comes to a slight boil. Lower heat slightly and cook until reduced to about 1/4 cup. Remove from heat and allow to cool completely (you can place it in the refrigerator to chill faster.)

Add butter and 2 cups of powdered sugar to bowl of an electric mixer. Beat until well combined. Add champagne and continue to mix until combined. Add 1 cup of powdered sugar along with heavy whipping cream and vanilla. Continue to beat until smooth, adding up to 1 cup of powdered sugar until you have reached the desired consistency.