Preheat your oven to 350 degrees
In a small bowl mix your flour, salt, and baking soda.
In a standing mixer or electric beater, cream your butter in another medium sized bowl. Start by mixing your butter on medium speed (any faster and the butter will heat up too much, leaving your cookie layer deflated), for approx 1 minute.
Now add your sugars (your white sugar in a steady stream on the side of the bowl, then plop your brown sugar in) and mix, on slow speed, until all of the sugar is added. Turn the speed up to medium and mix for about 1-2 minutes, or until the mixture has lightened and is slightly aerated. Turn the speed back down to low, and add the egg and the vanilla. Mix until ingredients are well combined.
Now slowly incorporate the flour mixture until everything just comes together. Turn off the mixer/electric beater and gently stir in your chocolate chips. Refrigerate until needed (cover beforehand if you are making the cookie dough hours in advance).
In another bowl, mix together your brownie mix according to the manufacturers instructions.
Grease an 8x8 or a 9x9 pan.
Pour in the brownie batter first. Smooth out the batter so it's even in your baking pan. Gently tap the pan on the counter a couple of times to release any bubbles.
Either using a tablespoon, regular spoon, or small ice cream scoop, spoon in dollops of cookie dough over the brownie batter. You'll probably won't use all the cookie dough (which means extra cookies for later...yay) but make sure the brownie batter is as evenly covered as it can be. Gently press the cookie dough into the brownie batter. Don't press too hard, you don't want to sink the cookie dough to far, but give the cookie dough a light press.
Now you're ready to bake. Put the pan into the oven and bake for 35-40 minutes, depending if you like your baked goods a bit under baked for maximum, delicious gooeyness, or if you like them fully cooked.
Pull the cookie brownies out of the oven and let stand 15 minutes before slicing up and serving.
Enjoy!!!!