Cream the Fats: In a large bowl, beat the softened butter and cream cheese together on medium speed for about 2-3 minutes until the mixture is light and fluffy.
Add the Sugars: Gradually add the brown sugar and granulated sugar to the butter mixture, beating on medium speed for another 1-2 minutes until well combined and slightly pale.
Mix in the Egg and Vanilla: Add the egg and vanilla extract to the sugar mixture, beating on medium speed for about 1 minute until fully incorporated and the mixture looks creamy.
Combine the Dry Ingredients: In a separate bowl, whisk together the flour, cornstarch, baking soda, and salt. Add this dry mixture to the wet ingredients and mix on low speed just until combined, taking care not to overmix.
Fold in Chocolate: Using a spatula or wooden spoon, fold the chocolate chips into the dough until evenly distributed throughout.
Preheat and Scoop: Preheat your oven to 350°F (175°C). Scoop dough onto baking sheets using a cookie scoop or tablespoon, spacing them about 2 inches apart.
Bake: Bake for 12-15 minutes, until the edges are lightly golden but the centers still appear slightly underdone.
Cool: Allow cookies to rest on the baking sheet for 5 minutes after removing from the oven, then transfer to a wire rack to cool completely.