• In the bowl of a stand mixer fitted with the paddle attachment or in a large bowl using a handheld electric mixer, beat the butter on medium speed until smooth and creamy.
• Add in the peanut butter and vanilla and beat until smooth, about 2 minutes.
• Next add in both sugars and beat until light and fluffy, scraping down the sides and bottom of the bowl as needed, about 2 minutes.
• Add in the eggs and yolk, one at a time, beating well after each addition. Turn mixer off.
• Add in the flour, oats, baking soda, baking powder, cinnamon, and salt. Whisk the ingredients together lightly before turning the mixer back on low and mixing in the dry ingredients until just combined. Be sure not to over mix here.
• Turn mixer off and use a spatula to fold in the M&Ms, chocolate chips, and peanuts. 
• Cover the bowl and place it in the fridge for 30 minutes, or up to 2 days. 

When ready to bake:

• Preheat oven to 350 degrees (F). Line two large baking sheets with parchment paper.
• Scoop two tablespoon sized mounds of dough onto the prepared cookie sheet, leaving a few inches between each cookies for spreading. Gently press down on each cookie ball, slightly flattening the ball. This will help them spread evenly in the oven. Sprinkle the top of each cookie with some extra oats, if desired. 
• Bake one tray at a time, for 12 minutes, or until the edges are golden and the centers have set. If any edges spread out while baking, use a spatula and gently press them back in as soon as you remove the cookies from the oven. 
• Cool cookies on the baking sheet for 10 minutes before transferring them to a cooling rack.