Mix Wet Ingredients: In a large mixing bowl, combine the melted and cooled unsalted butter, brown sugar, white granulated sugar, pure vanilla extract, and large eggs. Whisk vigorously for about 1-2 minutes until smooth.

Add Dry Ingredients: Carefully add all-purpose flour, cornstarch, baking powder, baking soda, and salt to the wet mixture. Fold together gently until just combined.

Fold in Chocolate Chips: Stir in both semi-sweet and dark chocolate chips evenly throughout the dough.

Prepare Baking Sheets: Preheat your oven to 350°F (175°C) and line two cookie sheets with parchment paper.

Scoop the Dough: Using a large cookie scoop, place six dough balls per cookie sheet, spaced out adequately.

Bake the Cookies: Slide one tray into the preheated oven and bake for 13-15 minutes until edges turn golden brown.

Cool and Enjoy: Allow the cookies to rest on the hot pan for 5 minutes before transferring to a cooling rack.