Soften vegan butter until it reaches near room temperature.
Whip butter with an electric mixer for 1 minute.
Add powdered sugar 1/2 cup at a time whipping for about 30 seconds between each scoop.
Add extract and continue to whip for 1 minute.
If needed, slowly pour in the plant-based milk while whipping the buttercream until the desired consistency is achieved. (This will vary depending on the type of vegan butter you used).
Video
Notes
Tips for making the perfect vegan frosting
Make sure your butter or chosen fats are just soft enough to whip, but not so soft that they are starting to melt.
Whip your frosting for a long time, at least 5 minutes total. Whipping the sugars and fats together will cause them to blend better and whip in air pockets that will make your buttercream light and fluffy.
Only add plant-milk if needed. You want your frosting to be smooth and creamy, yet firm enough to pipe perfectly.
If you struggle to make your piping look nice, I have found that this cupcake decorating tool is easier than piping bags for beginners. (I have no cake-decorating abilities at all, but it helps my cupcakes look so much better than when I use a piping bag).
For detailed piping with fewer air bubbles, whip for a total of 3-4 minutes.
For a lighter, fluffier frosting, whip for 5-6 minutes to allow for air to get trapped in the frosting and make it fluffier.
Flavor variations
Chocolate - add 1/3 cup cocoa powder along with the powdered sugar.
Strawberry - blend 1/2 cup of freeze-dried strawberries in a blender for about 1 minute until they turn to a powder and add to the frosting with the powdered sugar.
Mocha - add 1 tbsp of instant coffee to the butter and whip for one minute, let it sit for 5-10 minutes, then whip again. Add 1/4 cup cocoa powder along with the powdered sugar.
Lemon - add 1 tbsp lemon extract at the time you would add the milk (You may not need any milk with the liquid from the lemon extract).
Coffee - add 2 tbsp of instant coffee to the butter and whip for one minute, let it sit for 5-10 minutes, then whip it again. Add powdered sugar and follow the original recipe.
Mint - 1 tiny drop of food-grade peppermint essential oil, or 1/2 tsp of peppermint extract (or 3 tbsp creme de menthe).
Funfetti - add 2 tbsp of vegan sprinkles to the frostings after blending and fold in with a spatula. (See note on sprinkles below)
A cool trick for super silky buttercream
For the most amazing soft, silky, and creamy vegan frosting, replace the plant-based milk with 2 tablespoons of aquafaba. (This is the liquid from a can of chickpeas.) Be sure to continue to whip the buttercream on high for 5 full minutes after adding the aquafaba. The frosting may appear to separate for a minute after adding the liquid, but don't worry, it will come together again and produce the most amazing frosting texture ever! For the silkiest buttercream make my dairy-free whipped cream frosting.