Add the softened butter to a standing mixer or large bowl if using a hand held mixer. Then, mix the butter for 3-5 minutes until it is light and fluffy.Once it is fluffy, scrape down the bowl and add the cake mix and powdered sugar. Mix on low until it starts to incorporate.
It will start look crumbly but keep mixing and it will come together. Once it comes together, increase speed and continue beating another 3-5 minutes until it is very light and fluffy.If desired, add a tablespoon or two of milk or cream to get the frosting to your desired consistency and mix another minute.Use on your favorite dessert!