Whip the butter in a stand mixer with the whisk attachment until creamy and then add in half of the powdered sugar.
Mix in the milk, followed by the rest of the powdered sugar and vanilla extract.
Mix until well combined. The longer the better! (I usually do around 3-5 minutes). Taste the icing. If it’s not sweet enough for your liking, add in more powdered sugar. Increase milk and powdered sugar to keep the consistency of the icing nice and smooth!
Use icing right away or store in an airtight container in the refrigerator for 1 week or in the freezer for 6 months.