Step 1

Preheat oven to 350°F. Line two baking sheets with parchment paper.

Step 2

In a bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

Step 3

In a separate bowl, using a hand mixer or stand mixer fitted with the paddle attachment, beat butter and both sugars for 1-2 minutes, until light and fluffy. Add egg and vanilla extract, mixing until combined, scraping the sides of the bowl as needed. On low speed, add in flour mixture and mix until just combined.

Step 4

Gently stir in M&M's and chocolate chips. I usually add about 1 generous cup into the batter, and the rest get pressed on top of the cookies before baking.

Step 5

Place the sprinkles in a shallow bowl.

Step 6

Scoop balls of cookie dough, between 1½ and 2½ tablespoon portions. Gently press a few M&M's onto the top of each dough ball then press the top of each ball into the bowl of sprinkles. You can bake the cookies right away (they'll be on the thinner side) or chill the dough balls in the fridge for about 15 minutes to ensure they bake up with a nice thickness.

Step 7

Place dough onto prepared baking sheets leaving an inch or two for spreading. I like to make sure the dough balls are mounded higher rather than wider so that the cookies aren't too thin.

Step 8

Bake for 8-11 minutes (see note), until the edges of the cookies are set but the center is still slightly underdone; this will create a soft cookie. See note about shaping the cookies as soon as they come out of the oven.

Step 9

Place the baking sheets on wire racks and allow the cookies to cool completely. They will firm up as they cool.