Preheat the oven to 350°F (175°C).

Line an 8×8-inch baking pan completely with parchment paper, leaving enough overhang to lift the bars out after baking.

In a medium bowl, whisk together the flour, cornstarch, baking soda, and salt.

In a separate large mixing bowl, combine the melted butter, brown sugar, and granulated sugar.

Whisk for about 30 seconds until the mixture becomes smooth and slightly thick.

Add the eggs and vanilla extract.

Whisk for about 1 minute until fully incorporated and glossy.

Add the dry ingredients to the wet ingredients.

Gently fold everything together with a spatula until almost combined.

Reserve about ¼ cup of the chocolate chips for the top.

Fold the remaining chocolate chips into the cookie dough.

Transfer the dough to the prepared baking pan.

Spread it evenly into the corners while leaving a little texture on the surface.

Sprinkle the reserved chocolate chips evenly over the top.

Bake the Chocolate Chip Cookie Bars for about 50–55 minutes, or until the edges are golden and set.

Insert a toothpick into the center. It should come out with a few moist crumbs rather than wet batter.

Allow the bars to cool in the pan for about 1 hour.

Lift them out using the parchment paper, slice into squares, and serve