In a large mixing bowl, beat the softened butter until smooth and creamy.
Gradually add the powdered sugar, about one cup at a time, mixing on low speed to prevent sugar clouds.
Add the vanilla extract and a pinch of salt. Mix until combined.
Slowly add the heavy cream or milk, one tablespoon at a time, until the frosting reaches your desired consistency.
Beat on high speed for 2–3 minutes until light, fluffy, and spreadable.