Preheat your oven to 325 degrees F.
Sift together the flour, baking soda, and salt. Set aside.
In a medium bowl, mix melted butter, brown sugar, and white sugar until well blended.
Add the whole egg and beat for 2 minutes. Stop, scrape down the sides, and add the egg yolk and vanilla extract. Beat for an additional 2 minutes until lighter in color and thick.
Gently mix the dry ingredients until just blended. Avoid overmixing; you want to eliminate any flour streaks.
In an 11×7 baking dish, spread half of the cookie dough. Sprinkle 1 1/4 cups of chocolate chips over it. Add the remaining cookie dough and top with the rest of the chocolate chips.
Bake for 25-30 minutes. Let it cool for 10 minutes before digging in. We prefer our cookies slightly underbaked in the center, but if you like a firmer center, bake for 30-35 minutes. Keep in mind that the cookie continues to cook as it sits, so be cautious not to overbake. Enjoy your delightful cookie creation!