Preheat your oven to 325°F. Line 2 large baking sheets with parchment paper or silicone baking mats.
In a medium bowl, whisk the flour, baking powder, salt, and ground nutmeg. In a large bowl, use an electric mixer to beat the butter until light and fluffy. Add the granulated sugar and beat until well combined, light, and fluffy.
Add the room temperature egg and vanilla extract and mix until combined. In 2-3 additions, add the dry ingredients and mix until just combined after each. Then mix until the cookie dough comes together.
Take about 1 and ½ tablespoons of dough and roll it into a ball with the palms of your hand. Toss the dough in a bowl of sprinkles to generously coat all over. Repeat with the rest of the cookie dough and arrange the balls on your prepared baking sheets, about 2 inches apart.
Bake in the preheated oven, one baking sheet at a time, for 10-12 minutes*.
Take the cookies out of the oven and let cool on the baking sheet for at least 5 minutes before transferring to a plate or cooling rack.