Stir melted butter, brown sugar and granulated sugar until well combined.
Add in egg, egg yolk and vanilla. Mix until lighter in color.
Add in the flour, baking soda and salt. Scrape the sides of the bowl and the bottom really well to ensure a smooth, well stirred batter.
Hand stir the chocolate chips into the batter and let it sit 20 minutes to let the flour soak into the rest of the batter. (If your oven tends to run hot (aka flattens cookies) refrigerate the dough for 20 minutes).
Preheat oven to 325. Line two baking sheets with parchment paper and scoop cookie dough onto prepared pans, using a two tablespoon cookie scoop.
Bake 8-9 minutes, rotating sheets half way through baking. When you pull your cookies out of the oven, they will looked cooked around the edges and undercooked in the center.
Leave the cookies on the hot baking pans for 5-7 minutes or until you can remove them without falling apart. Place onto cooling racks and cool to room temperature before storing in air tight containers.