
Preheat oven to 350°F. Line two baking sheets with parchment paper.
In a bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
In a separate bowl, beat butter and both sugars for 1-2 minutes, until light and fluffy. Add egg and vanilla extract, mixing until combined. On low speed, add in flour mixture and mix until just combined.
Gently stir in M&M's and white chocolate chips. Scoop balls of cookie dough, between 1½ and 2½ tablespoon portions, and press the top of each ball into sprinkles.
Place dough onto prepared baking sheets leaving space for spreading. Bake for 8-11 minutes until the edges are set but the center is slightly underdone.
Allow cookies to cool completely on wire racks.