Butter a jelly roll pan. Place whole graham crackers on bottom, cutting to fit if necessary. Boil 1 cup butter, 1 cup brown sugar for 2 minutes. Remove from heat, spread over graham crackers. Bake at 350 degrees for 7 minutes. After removing from oven spread with a large Hershey bar and spread with a fork. Cut in squares when warm and put in refrigerator to firm up.