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

In a small bowl, whisk together the flour, baking powder, baking soda, and salt.

In a large mixing bowl, combine melted butter and granulated sugar. Whisk in the egg and vanilla until creamy.

Gradually fold the flour mixture into the wet ingredients. Then fold in white chocolate and rainbow sprinkles.

Scoop generous portions of dough onto the prepared baking sheet, leaving space between each.

Bake for 11-12 minutes until edges are golden but centers are soft. Add more sprinkles in the last 2 minutes.

Use a round cookie cutter to reshape them while warm. Cool for 10 minutes on the baking sheet before transferring to a wire rack.