In a large bowl, combine the ground beef, bread crumbs, milk, and onion soup mix, mixing until everything is evenly incorporated. Shape the mixture into 8 patties. This ensures that the ingredients bind together well, creating flavorful, cohesive patties that will hold their shape during cooking.
Heat oil in a large skillet over medium-high heat. Lightly dredge each patty in flour, coating it evenly, and then brown the patties on both sides in the hot skillet. This step creates a nice sear on the patties, adding flavor and texture while helping to lock in the juices before they finish cooking.
Place the browned patties into the slow cooker, stacking them alternately in a pyramid shape. This arrangement helps the patties cook evenly by allowing the heat and sauce to circulate around each layer, ensuring they stay tender and flavorful throughout the slow cooking process.
In a medium bowl, combine the condensed soup, water, and au jus mix, then pour the mixture over the beef patties. This creates a flavorful sauce that will infuse the patties as they cook, adding richness and depth to the dish.
Cook on low for 4 to 5 hours, or until the beef patties are fully cooked and tender. This slow cooking method allows the flavors to meld together, ensuring the meat is thoroughly cooked and infused with the savory sauce.