Preheat your oven to 325°F and grease a 9x13-inch baking dish.
In a large bowl, whisk together the melted butter, brown sugar, and granulated sugar until smooth.
Mix in the egg, egg yolk, and vanilla extract until well combined.
Add in the flour, baking soda, and salt. Stir until just combined—don’t overmix!
Fold in the chocolate chips gently.
Spread the dough evenly into the prepared baking dish.
Bake for 20–22 minutes, or until the top is golden and a toothpick comes out mostly clean.
Cool completely in the pan before slicing. (Or don’t. I won’t judge.)