Begin by combining your unsalted cold butter, brown sugar, and granulated sugar in a stand mixer or a large mixing bowl using a handheld mixer. Beat these ingredients on medium speed for 4–5 minutes until the mixture is light and fluffy.

Next, add the large cold eggs to the creamed mixture, one at a time. Mix on low speed, allowing each egg to fully incorporate before adding the next.

In a separate mixing bowl, whisk together the all-purpose flour, cornstarch, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet mixture on low speed. Mix until the dough comes together and is thick, about 30 seconds.

Gently fold in the semi-sweet and milk (or white) chocolate chips, and if using, add the nuts or espresso powder.

Using a large cookie scoop or your hands, form 8–10 large dough balls, each about 6 ounces, and place them onto a lined baking sheet.

Wrap the cookie dough balls tightly in plastic wrap and chill them in the refrigerator for 30 minutes to 1 hour.

While your dough chills, preheat the oven to 400°F (205°C) and prepare a parchment-lined baking sheet.

Remove the cookie dough balls from the refrigerator and place 3–4 on the prepared baking sheet. Bake for 9–11 minutes.

Allow the cookies to cool on the baking sheet for about 10 minutes, then transfer them to a wire rack to cool completely, or enjoy them warm right away.