In the bowl of a stand mixer fitted with the paddle attachment, cream the room temperature butter on medium speed until smooth and creamy. It should change from a yellow to a pale yellow.
Gradually add the powdered sugar, mixing on low speed until fully incorporated. Scrape down the sides of the bowl as needed to ensure all ingredients are well combined.
Add the vanilla extract and heavy cream to the butter mixture, then increase to medium-high speed. Beat until the frosting is light and fluffy, about 4-5 minutes.
If the frosting is too thick, add additional heavy cream, 1 tablespoon at a time, until it reaches the desired consistency. If it's too thin, add more powdered sugar, 1 tablespoon at a time.
Once the frosting is smooth and fluffy, it's ready to use!
Notes
Storage:Store any leftover Vanilla Buttercream in an airtight container on the counter for up to 2 days. It can also be frozen for up to 6 months and refrigerated for up to 1 week. Powdered Sugar: Sift if the powdered sugar is lumpy, recommended if piping. Heavy Cream:Heavy cream is recommended. The less fat in the milk the thinner the buttercream will be. I would recommend half and half if you don't have heavy cream. Using milk will can cause a grainy buttercream that separates.