- 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