In a 7-quart cast iron Dutch oven, heat shortening or bacon drippings over medium-high heat. Sauté cubed chicken 30 minutes or until dark brown on all sides and beginning to stick to bottom of pot. This process is important because jambalaya's brown color is derived from the color of the meat. Add smoked sausage and stir fry 10-15 minutes. Tilt pot to one side and ladle out all oil, except I large cooking spoonful. Add onions, celery, bell peppers and garlic. Continue cooking until all vegetables are well caramelized, being careful not to scorch them. Pour in stock, bring to a rolling boil then reduce heat to simmer. Cook 15 minutes to allow flavors to develop. Stir in mushrooms, green onions and parsley. Season with salt, cayenne pepper and hot sauce. If desired, slightly over-season dish since rice has not yet been added. Add rice, reduce heat to low, cover and cook 30-45 minutes. Stir every 15 minutes. Do not uncover except to stir.