Make sure the butter is very soft. (Let is sit out at room temperature for 1-2 hours if needed.) Set out an electric mixer with a paddle attachment. Place the butter in the bowl of the mixer.
Beat the butter on high for 2 minutes, until it's light and fluffy. Scrape the sides of the bowl with a rubber spatula.
Turn the mixer on low and add in 2 cups powdered sugar. Beat until incorporated, then add in the heavy cream, vanilla extract, and salt.
Scrape the bowl again. Then turn the mixer on low and slowly add in 3-4 more cups of powdered sugar. Once incorporated, turn on high for 1 minute to beat out all the clumps.
Turn the mixer back on low and mix in the sprinkles. Stop once they look even. If you beat the sprinkles too long, they will start to break. (Mix the sprinkles in with a spatula if your mixer does not have a very low setting.)
Video
Notes
Adapt for Holidays! You can use any color blend of jimmies in this recipe. Think black and orange for Halloween, or green and red for Christmas.