Preheat oven to 350°F. Prepare brownie mix as directed, and pour into a 9"x13" pan sprayed with cooking spray.
In a small bowl, beat cream cheese, milk, vanilla, and egg until creamy. Pour cream cheese mixture over brownie mixture. Sprinkle with chocolate chips. Bake for about 40 minutes. (Check at 30 minutes to see if it's done in the center, but continuing baking until mostly set.)
Let cool for best cutting, but they are yummy warm.