Saute onions, celery and mushrooms in margerine until tender, approximately 7 minutes. Combine all ingredients. Add egg last. Pour mixture into crockpot, cover, cook on high 45 minutes. Turn heat to low for 5 to 8 hours. Determine if you should use full amount of liquid by the moistness of the cubes. For large recipe 13 to 14 cups, double all ingredients except soup.