Preheat oven to 350 F. Line an 8×8 baking pan with parchment paper and set aside. Whisk together flour, cornstarch, baking soda and salt. Set aside.
In a separate large bowl, whisk butter, brown sugar and sugar until light in color, about 2 minutes. Add egg, egg yolk and vanilla.
Mix everything until combined, then fold the four into the wet mixture.
Stir in the chocolate chips by hand.
Transfer dough to prepared baking dish and press down evenly using a spatula or your hands. Bake for 25 to 30 minutes or until the edges are set and the center is soft.
Allow the cookie bars to cool in the pan for ten minutes prior to serving. Enjoy!
You can freeze the chocolate chip cookie bars for later, too!
Yummy! Enjoy the sweet, rich chocolate flavors of these gooey cookie bars.