
The Best Monster Cookies are loaded with peanut butter, oats, chocolate chips, and m&m's! They are thick, chewy, and a soft-baked cookie, with a surprise ingredient, that are crazy delicious.
Preheat oven to 350°. Line cookie sheets with parchment paper, use a silpat liner, or spray with cooking spray.
In a large bowl (or bowl of a stand mixer) cream together the butter, brown sugar, and peanut butter until light and fluffy, about 1-2 minutes.
Mix in the egg and vanilla, scraping down the sides of the bowl as needed.
In a separate bowl, add the flour, baking soda, cornstarch, baking powder, and salt and whisk to combine.
With the mixer on low speed, slowly add the flour mixture to the wet ingredients and mix until just combined.
Add the oats, chocolate chips, and M&M candies. Mix on low speed just until dough is combined.
Use a medium cookie scoop, or about 2 tablespoons cookie dough, and place on the baking sheets. They should look like golf balls.
Bake the cookies for 7-9 minutes until the edges are just starting to brown and the top still looks slightly undercooked.
Remove from the oven and cool for 5 minutes on the baking sheet before moving them to a wire rack to cool completely.
** These cookies don't spread much after baking. If you gently press additional m&m's onto the tops of each cookie that will help flatten the cookie to more of a "cookie shape". You can also tap the hot cookie sheet against the countertop or stove top to help the cookies to fall.