01 -
Whip butter in the bowl of a stand mixer using the whisk tool. Set it to medium-high until it fluffs up—about 3 minutes.
02 -
Mix in the vanilla extract.
03 -
Keep the mixer on low. Gradually pour in the powdered sugar, milk, and salt. Be sure to scrape down the bowl as you go.
04 -
When everything’s mixed, raise the speed to medium-high or high. Whip it for at least 3 minutes, but you can go up to 7 if needed.
05 -
If it’s too thick to spread, slowly add more milk while beating.
06 -
Keep it in the fridge for up to 2 weeks. Whip it again before spreading.