In a large bowl, beat the cream cheese and butter until smooth. Then add the powdered sugar and vanilla and beat just until combined and fluffy. Do not over mix. Add a Tablespoon or two of milk or heavy cream as needed.
Taste and add a pinch of salt and more vanilla if desired. You can also add 1/2 cup more powdered sugar if you'd like it a little sweeter or thicker. Or add more milk or cream if you want it more of a glaze consistency.
Store in the refrigerator for 3-5 days. Then spread over top of warm cinnamon rolls.