Place room temperature vegan butter in the bowl of a stand mixer fitted with the paddle attachment. Cream the butter until smooth and fluffy, 30-60 seconds.
Gradually add the sifted powdered sugar until fully incorporated, about 3 minutes. Start on the slowest speed, increasing as it comes together.
Add the dairy free milk and vanilla extract then mix on medium-high speed for about 1 minute, or until desired consistency is reached. For a thicker frosting, add a couple extra tablespoons of powdered sugar. If the frosting is too thick, thin it out by adding a couple tablespoons of dairy free milk.
Use immediately or store in the fridge for up to 1 week. Before decorating, make sure the dessert is cooled completely.
Notes
This makes enough dairy free frosting to decorate 24 cupcakes or two 8-9-inch round cakes.