Pre-heat your oven to 350° F and line your baking sheets with parchment paper.
In a sauce pan over medium high heat, add your butter and let melt. Once it's melted keep it on the heat and let it cook for 5-10 minutes until it foams up and then turns brown. Let cool.
In a large bowl add your brown butter, brown sugar and sugar. Stir together until well combined and light and fluffy.
Add your eggs and vanilla extract and whisk until foamy and smooth in texture.
Once your wet ingredients are combined, add your flour, cornstarch, baking soda & salt and fold until it forms a dough.
Add your oats, chocolate chips, Christmas m&ms, chopped pecans, chopped Oreos and chopped Reese’s (or whichever add ins your using) and fold until evenly distributed.
Scoop your dough into 1-2 inch balls and place on your baking sheets lined with parchment paper. Top with more add ins.
Bake at 350° for 8-10 minutes on cookie sheet at a time. Remove from oven once golden brown. Make sure you under bake rather than over bake as the cookies with continue to cook a little and set once they are removed from the oven.
Let cool, sprinkle with flaky sea salt if desired, share and enjoy!!
