In a stand mixer, combine the butter and sugar for about three minutes until light and creamy. Add the egg, scraping the bowl as needed.

Add the flour, baking powder, salt, and vanilla to the bowl and mix on low just until the dough comes together. Spoon the dough onto two pieces of plastic wrap.

Roll each of the dough mounds into logs, using the plastic wrap to help. Place the cookie dough (wrapped at this point) in the refrigerator for at least 30 minutes or several hours.

When ready to make cookies, preheat the oven to 350F and prepare baking sheets with baking mats or parchment paper. Sprinkle sprinkles or sugar onto a large plate (this step is optional). Unwrap the dough logs and roll in the sprinkles, pressing to help as many as possible stick. Slice the cookie dough into ⅓ inch slices and place 2 inches apart on the baking sheet.

Bake the cookies for 8-10 minutes until just barely golden. The cookies will be soft in the center and have hardly any color. Allow the cookies to cool on the baking sheet for 10 minutes, then remove to a rack to cool completely. Enjoy!