Melt the butter over medium heat, stirring constantly. If you're going to brown it make sure you only brown the butter lightly.
In a large mixing bowl combine the butter and brown sugar. Beat until mixed together. Add in the egg, egg yolk, and vanilla extract. Mix well.
Add the flour, salt and baking soda and beat until well mixed. Add the oats and beat to combine.
Last add the chocolate chips, folding to distribute them evenly.
Refrigerate the cookie dough for at least a half hour, or overnight.
When you are ready to bake the cookies, preheat the oven to 350°F and line a cookie sheet with parchment paper. Use a 1 ounce cookie scoop to scoop the cookie dough out into balls, placing them 2 inches apart on the prepared sheet. Bake for 11 minutes*, or until the edges are just golden brown and the centers have puffed up but are still gooey.
Allow to cool before eating!
