Preheat oven to 375°F. Line cookie sheets with parchment paper or silicone baking mat.
Mix butter, 1/2 cup powdered sugar, and vanilla with an electric mixer. Add flour and salt and mix until a smooth dough forms. Stir in the sprinkles. If dough is too soft, chill it until you can work it easily with your hands without sticking.
Scoop dough into 1 tablespoon portions and roll into balls. Place on prepared cookie sheet.
Bake cookies for 7-10 minutes until bottoms are just slightly golden.
Remove from oven and cool for 1 minute until you can handle them. Drop into a bowl (or gallon size zip top bag) of powdered sugar and roll each cookie in the sugar until coated. Place on a rack to cool completely.
Re-roll in powdered sugar before serving if desired. Store in a sealed container.