Preheat your oven to 325 degrees F. Prepare a cooking sheet with non stick cooking spray or parchment paper and set aside.
Cream together melted (and slightly cooled) butter with sugar and brown sugar in a stand mixer or in a large bowl with a hand mixer until well combined. Next beat in vanilla, cinnamon, egg, and egg yolk. Beat together for 2-3 minutes until smooth and creamy.
n a separate bowl shift together flour, salt, and baking soda. Slowly mix this with your wet ingredients until well combined. Last fold in oats and mini Baking M&M candies. Serve them and enjoy!
Roll out balls of dough and place them on your prepared baking sheet. Bake for 10-12 minutes. Allow to cool for 3-4 minutes on the baking sheet before moving it to a cooling rack.