Prepare the brownie layer-
Preheat the oven to 350 degrees F. Spray a 9x9-inch pan with nonstick spray, then line with a strip of parchment paper so that it covers the bottom and comes up two sides of the pan. Spray the parchment with nonstick spray too.
In a microwave safe bowl (or in the top of a double boiler or pan set on top of a pan of simmering water), microwave in 30 second bursts to melt butter and chocolate chips together until all is melted and smooth. Whisk in the sugars, then whisk in the eggs, vanilla and salt.
Prepare the cookie dough layer:
Sprinkle in the flour and mix in until combined. Stir in the 1 cup of chocolate chips. Scoop the cookie dough onto the top of the brownies and spread onto the brownie layer. I find that it's easiest to do this if the brownie layer is chilled and firm. Wet your hands or spray them with nonstick spray and pat the cookie dough on top in a even layer.
Sprinkle additional chocolate chips on top to create a nicer, visual appearance. For easy, clean cutting, chill the brownies (wrap the brownies with plastic wrap and chill until firm- 1 to 2 hours or up to 2 days).
Slice the brownies with a sharp knife, wiping the knife with a paper towel between cuts. If you'd like all of your slices of brownies to look clean-cut without edges, use the knife to cut the sides of the brownies off before cutting pieces.