Place the browned beef patties on top of the sliced onions in the slow cooker, stacking them alternately. In a separate bowl, stir together the 2 (10 oz) cans condensed cream of chicken soup, ¾ cup water, and the 1 (1 oz) packet au jus mix until smooth. Pour this gravy mixture over the beef patties. Cover and cook on LOW for 4-5 hours, or until the beef is cooked through and the patties are tender.

Serve this Slow Cooker Salisbury Steak with mashed potatoes or egg noodles to soak up all that delicious gravy!