In a large mixer bowl, beat butter & sugar at medium speed until fluffy, scraping sides as needed.
Beat in egg & extract.
Add flour & salt to butter mixture, beating just until combined.
Shape dough into 1-inch balls; roll in sprinkles.
Place on a paper plate & flatten slightly with the bottom of a glass.
Top with a pinch of additional sprinkles
Freeze until firm, approximately 15 minutes.
While the dough is chilling, preheat oven to 350° & line baking sheets with parchment paper.
Remove from freezer & place at least 2 inches apart on prepared pans.
Bake until edges are lightly browned, 12 to 15 minutes.
Let cool on pans 2 minutes.
Remove from pans, & let cool completely on wire racks.
Store in airtight containers up to 3 days.