2 cups powdered sugar
1/2 cup unsalted butter, softened
2–3 tablespoons milk or heavy cream
1 teaspoon vanilla extract
Pinch of salt
Beat the butter until smooth
Add the powdered sugar gradually
Mix in the vanilla extract and salt
Add milk or cream one tablespoon at a time
Beat until light and fluffy
Adjust thickness with more sugar or more milk
Spread or pipe onto cooled cake