Start by cutting the cold unsalted butter into small cubes, then cream it together with brown and granulated sugars in a stand mixer on medium speed for 4–5 minutes.

Continue mixing until light and fluffy, then gradually add the cold large eggs, mixing well after each addition.

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

Gradually add the dry ingredients to the wet mixture while mixing on low speed, stopping when just combined.

Gently fold in both the semi-sweet and milk chocolate chips, along with any chopped nuts if desired.

Using a large cookie scoop or your hands, form 8-10 large, uneven dough balls, each roughly 6 ounces.

Chill the portioned dough on a baking sheet in the refrigerator for 30–60 minutes.

Preheat your oven to 400°F (205°C) and place 3–4 dough balls on a parchment-lined baking sheet.

Bake the cookies for 9–11 minutes until the tops are golden and the edges are set.

Allow the cookies to cool on the baking sheet for about 10 minutes before transferring them to a wire rack.