Brown the butter on the stove while stirring continuously. Set aside and allow to cool.
In a mixing bowl combine browned butter, brown sugar, egg, egg yolk, and vanilla extract. Stir until well combined.
Add in flour, baking soda, old fashioned oats and salt. Stir together with the brown sugar mixture. Lastly, add in the chocolate chips. Adjust the amount of chocolate depending on your taste.
Refrigerate dough for 30min to 1 hour to stiffen up.
Place balls of dough onto the cookie sheet. Bake at 350 degrees for 15 minutes, or until golden brown.
