Step 1

Place 2 sticks unsalted butter in the bowl of a stand mixer (or large bowl if using an electric hand mixer). Let sit at room temperature until softened. Meanwhile, place 2 1/2 cups all-purpose flour, 2 teaspoons cornstarch, and 1 teaspoon baking soda in a medium bowl. Whisk to combine.

Step 2

Add 1 cup packed brown sugar, 1/2 cup granulated sugar, and 1/2 teaspoon kosher salt to the bowl of butter. Beat with the paddle attachment, starting on low speed and gradually increasing to medium-high speed, until light and fluffy, 2 to 3 minutes. Scrape down the sides of the bowl with a flexible spatula.

Step 3

Add 2 large eggs and 2 teaspoons vanilla extract, and beat on medium speed until combined, about 90 seconds. Scrape down the sides of the bowl. With the mixer on low speed, gradually add the flour mixture and beat until just combined and no streaks of flour remain.

Step 4

Add 1 1/2 cups of the semi-sweet chocolate chips and fold into the dough with a flexible spatula.

Step 5

Line a rimmed baking sheet with parchment paper or a silicone baking mat. Scoop the dough out into level 2-tablespoon portions (about 40). Roll into balls. The dough balls can be close together on the baking sheet, just not touching. Gently press the remaining 1/2 cup chocolate chips into the top of dough balls (3 to 4 per cookie).

Step 6

Completely wrap the baking sheet in plastic wrap. Refrigerate for 12 to 24 hours.

Step 7

Arrange 2 oven racks to divide the oven into thirds and heat the oven to 350℉. Line 2 rimmed baking sheets with parchment paper or silicone baking mats. Place the dough balls at least 2 inches apart on the baking sheets, 12 per sheet.

Step 8

Bake for 6 minutes. Rotate the baking sheets between racks and from front to back. Bake until the tops of the cookies are set and edges are golden-brown, 5 to 7 minutes more. Let cool for 5 minutes on the baking sheet. Transfer the cookies to a wire rack and let cool completely. Repeat baking the remaining dough balls on cooled baking sheets; you can reuse the parchment or baking mats.