01 -
Preheat oven to 350°F (177°C). Line baking sheets with parchment paper or nonstick baking mats.
02 -
In a large mixing bowl, using an electric mixer or stand mixer fitted with a paddle attachment, cream together softened butter, brown sugar, and granulated sugar until light and fluffy, about 2 to 4 minutes.
03 -
Add peanut butter, vanilla extract, eggs, and egg yolk to the bowl. Mix until fully combined, scraping down sides as needed.
04 -
In a separate medium bowl, whisk together all-purpose flour, baking soda, and baking powder until evenly blended.
05 -
Add dry ingredients to wet mixture. Mix on low speed until just combined and a cohesive dough forms. Stir in M&Ms and mini chocolate chips until evenly distributed.
06 -
Using a large cookie scoop, portion dough into balls, approximately 3 tablespoons each. Arrange on prepared baking sheets, spacing 2 inches apart.
07 -
Bake for 12 to 13 minutes, or until edges are lightly golden. Do not overbake to preserve chewy texture.
08 -
Remove cookies from oven. Optionally, sprinkle with flaky sea salt. Allow to cool on baking sheets for several minutes before transferring to a wire rack.