Place the ½ cup unsalted butter or vegan baking stick in a heat safe bowl. Place a paper towel on top of the bowl so the butter doesn't splatter. Microwave in 11 second increments until just melted. Do not let it bubble or brown. Set aside to cool.
In a medium bowl, whisk together the 1 ¾ cups gluten free flour, 1 teaspoon baking soda and ½ teaspoon kosher salt. Set aside.
In a small bowl, using a spoon, mix together the 2 heaping tablespoons of cornstarch and the 3 tablespoons of water until thin and watery. It will be thick and tacky at first.
Into the cooled melted butter, combine the 1 ¼ cups light brown sugar, the cornstarch water and the 1 teaspoon pure vanilla extract. Whisk until it is all fully emulsified and blended. It may appear slightly chunky. That's normal.
Starting and ending with the flour mixture, whisk half the flour into the melted butter mixture. Then add the ¼ cup milk and whisk to combine. Add in the second half of the flour gently with a spatula. Do not over mix or the dough will become shiny and too sticky.
Still using the spatula, scrape down the sides of the bowl and fold in 1 ¼ cups of chocolate chips. Gently fold until everything is just combined and you don't see any more flour. Again, make sure not to over mix.
The dough will be very sticky. Add it to a freezer safe bowl, cover the top with plastic wrap and pop the entire bowl of dough in the freezer for 30 min.
When the dough is almost done chilling, preheat your oven to 350 degrees Fahrenheit and line a baking sheet with parchment paper. Do not grease.
Take the dough out of the freezer. Using an ice cream scoop or large cookie scoop (I use a 2 ounce cookie scoop), scoop the dough out into 14 scoops.
Pour the additional ½ cup chocolate chips into a small bowl. Press the tops of the dough balls into the chocolate chips. With your hand, gently press down on the chips so they stick to the dough, but keep the ball shape.
Place the dough balls about 3-4 inches apart on the parchment lined baking sheet. Bake the cookies at 350 degrees Fahrenheit for 13 minutes.
Immediately reshape the cookies when they come out of the oven. Use a spatula to push them into a circle and let cool on the baking sheet for 5 min before transferring to a cooling rack. If you don't let them cool a little on the pan, the cookies will break apart into a giant mess when you try to lift them up. Repeat this with the remaining dough balls.