01 -
Preheat oven to 325°F (163°C). Line a large baking sheet with parchment paper or a silicone baking mat.
02 -
Using a mixer, beat the butter, granulated sugar, and brown sugar until combined and creamy.
03 -
Add the beaten egg, vanilla extract, and peanut butter; beat until combined. Scrape the bowl as needed.
04 -
In a separate bowl, whisk together the flour, oats, baking soda, and salt.
05 -
Beat the dry ingredients into the wet ingredients on low speed, then mix in the M&Ms, chocolate chips, and other add-ins.
06 -
Shape the dough into one large mound (giant cookie) or 4 smaller mounds (smaller cookies).
07 -
Bake until edges are lightly browned. See recipe details for baking times for giant vs. smaller cookies.
08 -
Cool on the baking sheet. Press extra chocolate chips and Valentine's candies into the top while warm.
09 -
Enjoy your giant (or smaller!) Valentine's Day Monster Cookie!