Whisk together the melted butter, brown sugar and granulated sugar until combined. Add the egg, egg yolk and vanilla extract and whisk until combined.
Add the flour, baking soda, baking powder and salt to the wet ingredients and slowly fold together until a dough forms. Add the chocolate chips and fold until fully incorporated.
Space the cookies 3-4 inches apart on a large baking sheet lined with parchment paper.
Bake for 12-13 minutes until the edges are set and lightly golden and still soft in the center. These cookies are best enjoyed when still slightly warm and the chocolate chips are all melty!