Preheat the oven to 350°F (180°C) and line a baking tray with parchment paper. Set aside.
Add softened butter and light brown sugar to the bowl of your stand mixer and cream them together until smooth.
Add milk and vanilla extract and mix in.
In a separate bowl add flour, baking soda, baking powder, cornstarch and salt and mix them together.
Then add all your dry ingredients in with your wet ingredients and mix it into a cookie dough. Use a spoon for this, don't use your electric mixer.
Add chocolate chips and mix in.
Break off pieces of the dough and roll them into balls. Place them evenly on a parchment lined baking tray. Aim to get 20 cookies out of the batch.
Bake for 10-12 minutes until lightly golden on top.
As soon as they come out of the oven, press more chocolate chips directly into the tops of the warm cookies.
The cookies will be soft when they come out of the oven but will firm up as they cool. Let them cool and firm up directly on the baking tray before moving them.