1-2tbspmilk, optional(add to thin buttercream if too thick)
Instructions
Using a hand or stand mixer, beat the butter for about 2 minutes on medium-to-high speed. Scrape down the sides of the bowl.
Slowly add the powdered sugar and vanilla. Mix on low speed until incorporated, then increase your speed and mix well for about 5 minutes. Scrape down the bowl as needed.
Add the marshmallow fluff and mix on medium-to-high speed for another 2 minutes, scraping the bowl as needed. If buttercream seems too thick, add milk one tablespoon at a time until desired consistency is reached.
Use immediately or refrigerate until needed. Leftover buttercream can be frozen for up to 3 months.