I used to make the Duncan Hines Butter Fudge Brownies whenever I had a test in college. My roommates always knew my stress level by the particular smell of the apartment.
It was super simple:
1 box Duncan Hines Butter Fudge Cake Mix
2 eggs
1/2 cup butter or margarine, melted
1 cup chocolate chips
1 cup chopped pecans or walnuts (optional)
Preheat oven to 350 degrees. Grease 13x9-inch pan.
Stir first three ingredients together (like traditional brownie mix). Then stir in chocolate chips and optional nuts. Spread batter into pan. It will be a little thick so press to ends but don't overwork batter. It will spread out because of butter anyway. Bake for 25-35 minutes. Test for doneness.