Make 1 1/2 recipes of my Basic Creamy Buttercream frosting in order to have enough to fill and frost the entire cake. Recipe attached below. Use 1 1/2 cup butter and 6 cups confectioner's sugar, adding more cream as needed, see tip in recipe for perfect light creamy frosting
https://cookpad.com/us/recipes/367337-basic-creamy-vanilla-buttercream-frosting