Beat 1/2 cup of room-temperature butter on a medium speed for 30 seconds with a paddle attachment until smooth.
Mix in 1 1/2 tsp vanilla extract and 1/4 tsp fine salt on a low speed.
Slowly mix in 1 1/2 cups of powdered sugar on a low speed. Halfway through add 1 Tbsp of heavy cream to make the frosting easier to mix.
Mix on low for a couple of minutes until the ingredients are fully incorporated and the desired consistency is reached.
If the frosting is too thick, add additional cream (1 Tablespoon at a time). If the frosting is too thin, add in more powdered sugar (1/4 cup at a time).
Place the buttercream in a piping bag fitted with your favorite piping tip (I used a Wilton 1M). If you don’t have any frosting bags and tips, use a freezer Ziplock bag and trim the corner to have a 1-inch opening.
The last step is to decorate these cupcakes! Pour your favorite sprinkle blend into a small bowl (I combined 3 different types of rainbow sprinkles to make my own blend). Then, pipe a buttercream rosette of frosting onto each cupcake. Start in the center, then pipe a swirl out toward the edges of the cupcake.
Gently dunk the edges of the cupcake into the sprinkles, then enjoy!