Start by placing the softened butter in a large mixing bowl. If you’re using a stand mixer, fit it with the paddle attachment. Beat the butter on medium speed until it’s creamy and lightened in color, about 2 minutes.
Gradually add the powdered sugar to the creamed butter. It’s best to add about half a cup at a time, beating well after each addition. This method prevents the sugar from flying everywhere and helps it incorporate evenly into the butter.
Once all the sugar is mixed in, drizzle in the vanilla extract.
Check the consistency of your frosting after you’ve added the initial 2 tablespoons of milk or heavy cream. If it’s too thick, add more liquid, one tablespoon at a time, until smooth.