Place room temperature butter in mixer and whip until fluffy. Add the salt and mix, then add the vanilla and mix until thoroughly combined.
Slowly add the confectioners' sugar one cup at a time, mixing in between each cup. Add 2 tablespoons of milk. Mix. Add additional tablespoons of milk, one at a time, until desired consistency is reached.
Note: If icing becomes too thin, add more confectioners’ sugar. If it’s too stiff, add another tablespoon of milk.