Melt the white chocolate chips in a heatproof bowl by microwaving them in 30-second increments, stirring between each one, until they're completely melted. Alternatively, melt them using a double boiler on the stove, stirring constantly until smooth.Set the melted white chocolate aside to cool slightly.
Use an electric mixer to cream the dairy-free butter in a large bowl.Gradually add in the powdered sugar, one cup at a time, until you've reached your desired sweetness and consistency.Add the melted white chocolate and vanilla extract to the bowl, and beat everything together until well combined.
If the frosting is too thick, add a bit of dairy-free milk. Start with just a tablespoon or two, and add more as needed until you've reached your desired consistency.Once the frosting is the right texture, it's ready to use! Spread it onto cakes or cupcakes using a spatula, or pipe it onto your baked goods using a pastry bag and decorating tip.Store any leftover frosting in an airtight container in the fridge for up to a week. Before using it, let it come to room temperature and give it a quick stir to loosen it up. Enjoy!