Mise en place. Make sure butter and cream cheese are softened.
Whip together cream cheese, butter, vanilla, and milk. Whip until completely smooth and a little fluffy.
Add 1 C. powdered sugar and all of cinnamon. Whip in until completely smooth.
Add rest of powdered sugar, 1/2 C. at a time, until at desired sweetness. Whip completely until smooth and frosting is light and fluffy.