Preheat your oven to 350°F (175°C). This ensures that your cookies bake evenly and achieve that perfect crispy texture.
Line a baking sheet with parchment paper. This will prevent the cookies from sticking and make cleanup a breeze.
In a mixing bowl, combine the all-purpose flour, cornstarch, baking soda, and salt. Whisk them together until well blended.
In a separate bowl, mix the melted butter, granulated sugar, brown sugar, egg yolk, nonfat milk, and vanilla extract. Whisk until smooth and creamy.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix, as this can lead to tough cookies.
Gently fold in the mini chocolate chips with a rubber spatula, ensuring they are evenly distributed throughout the dough.
Using a cookie scoop or spoon, drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake the cookies in the preheated oven for about 10-12 minutes, or until the edges are golden brown and the centers look slightly soft.
Once baked, remove the cookies from the oven and let them cool on the baking sheet for 5 minutes before transferring them to a cooling rack to cool completely.