Preheat oven to 350 degrees F (180 degrees C). Cover cookie sheet with foil. Spray foil with cooking oil spray. Place crackers on foil in 5x7 inch rows.

Microwave butter on high for 2 minutes. Add brown sugar and stir. Microwave on high for 2 more minutes, stirring every 30 seconds. Pour over crackers.

Bake 17-20 minutes (should bubble but not burn). Sprinkle chocolate chips over hot crackers. Spread over 2 minutes (chips will have softened). Sprinkle nuts on top. Refrigerate 1 hour. Break into pieces. Can be frozen.