Preheat oven to 350 degrees. Lightly grease a 9×9 pan.
In a large bowl, combine the butter, sugar, & vanilla. Beat in the eggs.
Combine flour, cocoa powder, & salt. Add a little at time to the egg mixture just until combined. Fold in chocolate chips and pour into prepared pan.
Bake about 22-26 minutes or just until done (do not overbake). Remove and cool.
COOKIE DOUGH LAYER
Cream butter, white sugar and brown sugar with mixer on med-high. Add in milk. Add in flour a bit at a time until fully incorporated. Stir in chocolate chips with a spoon. Spread mixture over cooled brownies.
Bring heavy cream and butter just to a boil. Pour over chocolate chips and let sit 4 minutes without stirring. Stir until completely combined.
Pour over the cookie dough layer. Let cool at room temperature for 30 minutes (this keeps the topping shiny). Refrigerate to set.