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

Combine peanut butter, brown sugar, and granulated sugar in a large mixing bowl and blend until light and fluffy.

Add the egg and vanilla extract and mix on low speed until fully incorporated.

Sprinkle in baking soda and salt, then mix gently until combined.

Fold in M&M’s, reserving a few for topping.

Scoop dough onto the baking sheet, leaving space between each cookie.

Flatten each dough ball and press reserved M&M’s on top.

Bake for 8-10 minutes until edges are set but centers are soft.

Let cool for 5 minutes on the baking sheet before transferring to a wire rack.