Preheat your oven to 350°F (175°C) and line two standard baking sheets with parchment paper. Set aside. In a stand mixer fitted with the paddle attachment, cream together the cold cubed unsalted butter, dark brown sugar, and granulated sugar on medium speed until smooth, about 2–3 minutes. Use a rubber spatula to scrape down the sides and bottom of the bowl. Add the egg and mix on medium speed for 30 seconds, then stir in the vanilla extract just until combined.

Add the baking soda, baking powder, cornstarch, salt, all-purpose flour, and chocolate chips. Mix on low speed just until everything is incorporated. Using a 3-tablespoon cookie scoop, portion the dough and, while the dough is still in the scoop, press a caramel into the center. Release the cookie dough onto the prepared baking sheet. Each sheet will hold about six cookies, spaced approximately 2 inches apart.

Bake the cookies in the preheated oven for 10–12 minutes, or until the edges turn golden brown. The centers might look slightly underbaked but will continue to firm up as they cool. For an extra touch, sprinkle flaky sea salt over the cookies right after baking. Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.