In the bowl of a stand mixer fitted with the paddle attachment or in a large mixing bowl using a handheld mixer, beat the butter until smooth.
Add the powdered sugar and mix on low speed at first, then increase to medium speed and continue mixing for 1 to 2 minutes or until fully combined.
Add the heavy cream (start with 2 tablespoons and add a little more if needed), vanilla extract, and salt and continue mixing on medium speed until everything is well combined, stopping to scrape down the sides of the bowl as needed.
Use the frosting to pipe onto cupcakes or frost a cake or cover tightly and refrigerate until you are ready to use it.
Recipe Variations:
Vanilla: For a vanilla buttercream frosting, I like to add an additional teaspoon of vanilla extract to amp up the vanilla flavor.
Chocolate: Sift 1/2 cup (40 grams) of unsweetened cocoa powder and mix it into the frosting base until well combined. Add 1 to 2 extra tablespoons of heavy cream if needed for a smoother, creamier frosting. For a sweeter frosting, mix in an additional 1/2 to 1 cup (60 to 120 grams) of powdered sugar.
Caramel: Mix in 1/3 to 1/2 cup of homemade or store-bought caramel sauce. For a salted caramel frosting, you can use salted caramel and omit the salt in the recipe.
Strawberry: Add a 28 g bag of freeze dried strawberries to a blender or food processor and process until the berries are crushed into a fine powder. Mix the freeze dried strawberry powder into the frosting base until well combined.