Cream together unsalted butter and granulated sugar until light and fluffy. Beat in egg and vanilla extract.

In a separate bowl, whisk together flour, baking powder, and salt. Gradually mix dry ingredients into wet ingredients until a soft dough forms. Fold in chocolate chips if using.

Divide dough in half, shape into logs, wrap tightly, and chill in the refrigerator for at least 2 hours.

Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.

Remove logs from the refrigerator, roll in sprinkles if desired, and slice into ¼-inch rounds.

Bake slices for 10-12 minutes until edges are lightly golden. Let cool on baking sheets for 5 minutes before transferring to wire racks.