Preheat oven to 350. Spray bottom of large bar pan (15 1/2 x 10) with cooking spray.
Prepare brownie mix according to directions on box. Pour prepared mix into bar pan and bake for 15 minutes.
Meanwhile prepare the chocolate chip cookie dough. In a small bowl stir together flour, baking soda and salt. Set aside. Cream butter and sugars til light and fluffy. Add vanilla and egg. Beat well. Add dry ingredients to creamed mixture. Mix well. Add semi-sweet chocolate chips. Mix well.
Using waxed paper roll cookie dough out into a 15 1/2 x 10 rectangle. Remove brownie from oven and invert cookie dough onto brownie (remove waxed paper). Increase oven temp to 375 and return bar pan to oven. Cook for an additional 15 minutes or until cookie on top is golden brown. Cool completely. Cut into squares and serve!