Preheat the oven to 350°F and line a large 12x17-inch jelly roll pan with parchment paper and spray with nonstick cooking spray. Set aside.
In a medium bowl, whisk together the 2¼ cups all-purpose flour, 1 tablespoon cornstarch, 1 teaspoon baking soda, and 1 teaspoon salt. Set aside.
2¼ cups all-purpose flour, 1 tablespoon cornstarch, 1 teaspoon baking soda, 1 teaspoon salt
In a large bowl with a hand mixer or a stand mixer fitted with a paddle attachment, cream together the 1 cup unsalted butter, 1 cup light brown sugar, ¾ cup granulated sugar, and 1 teaspoon vanilla extract for 2 minutes until pale.
1 cup unsalted butter, 1 cup light brown sugar, ¾ cup granulated sugar, 1 teaspoon vanilla extract
Add the 2 large eggs, one at a time, mixing after each addition just until combined. Scrape down the sides of the bowl as needed.
2 large eggs
Add the flour mixture to the butter mixture and mix just until combined.
Mix in the 2 cups chocolate chips.
2 cups chocolate chips
Spread the cookie dough out on the parchment-lined jelly roll pan and use your hands or a rubber spatula to spread the dough all the way to the edges. It might seem like there isn't enough dough, but trust me, there is.
Bake for 17 to 20 minutes. The edges should be a nice golden brown, the cookies should look a little ripply, and the center will still be soft. Allow the cookies to cool for 20 to 30 minutes in the pan before using a pizza cutter to slice them into squares.5