Preheat oven to 350 degrees F. Line a baking sheet with parchment paper and spray with nonstick cooking spray. Pull butter out of fridge and sit on counter if you haven't already.

For the Brownie Batter: Add the chocolate chips and butter to a microwave safe bowl and microwave on low power, stirring every 30 seconds, until melted. Then mix in the sugar, flour, milk and cocoa powder, plus a pinch of salt (if desired). Set aside.

For the Chocolate Chip Cookies: Whisk together the flour, baking soda and salt together in a bowl and set aside. Cream the butter and sugar in the bowl of a stand mixer secured with the paddle attachment (or in a large bowl with a hand held mixer). Beat on medium-high for 2 minutes or until light and fluffy. Add the egg and vanilla and beat until just mixed in. Then add the dry ingredients and mix until they are just incorporated (try not to overmix).

Break the cookie dough into 10 even pieces and roll into a ball with your hands. Place them at least 2 inches apart on the baking sheet then flatten then.

Divide the brownie batter into 5 parts, about 15g each, roll into a ball, then flatten into a disc. Place on top of 5 of the cookies.

Place the remaining 5 cookies on top of the brownie batter. Secure the sides so they all stay together.

Bake for 10 minutes or until golden brown along the edges. Then take out and transfer to a wire rack to cool.