Allow 1 cup butter to come to room temperature.
Mix butter at medium high speed for 4 minutes.
Reduce speed to low, gradually add in powdered sugar.
After powdered sugar has been fully integrated into butter, add vanilla extract. Increase speed to medium high for 2 minutes.
Reduce speed to low, gradually add in milk until frosting attains desired consistency. If frosting remains too thick, gradually add additional milk 1 tbsp at a time.
Mix on medium high for 2 additional minutes.