Christmas Monster Cookies are soft, chewy, and made extra festive with the addition of red and green M&Ms. An oatmeal batter is studded with peanut butter chips, chocolate chunks, and candies, perfect for cookie platters, holiday exchanges, and gifting!
Preheat your oven, and line baking sheets with parchment paper or silicone mats.
In a large mixing bowl, cream the softened butter, dark brown sugar, and granulated sugar until light and fluffy. Then, beat in the egg, egg yolks, and vanilla until well combined.
In a separate bowl, whisk all the dry ingredients except the mix-ins until smooth.
Working slowly, add the dry ingredients to the bowl of wet ingredients, and mix just until combined. Fold in the mix-ins.
Use a cookie scoop or spoon to portion the dough into balls. Place the cookie dough balls on the prepared baking sheets, leaving space in between.
Transfer the cookies to the oven, and bake just until the edges are lightly golden.
Allow the cookies to cool slightly. Then, transfer them to a wire rack to cool completely.