Line a 9x11 pan with parchment paper and spray the sides that aren’t lined.
In a separate bowl whisk the flour, baking soda, and salt. Set aside.
Using a handheld or stand mixer fitted with a paddle attachment, beat the butter, brown sugar, and granulated sugar together in a large bowl on medium-high speed until combined and creamy, about 2 minutes. Add egg, vanilla extract, then beat on medium-high speed until combined. Scrape down the sides and up the bottom of the bowl as needed.
Beat in the dry ingredients on low speed, then beat in the chocolate chips until combined.
Using a cookie scoop divide into 15 equal balls and add the cookie dough on top of the brownies.
Press down the cookie dough with a spoon.
Bake for about 30 minutes. Using a toothpick, test to make sure it comes out with fudgy remains on the toothpick and the top looks dry. Do not over bake them.
Let it cool completely and cut into squares.