In a large mixing bowl, use your hands to mix together ground beef, onion soup mix, breadcrumbs, and milk. Once thoroughly mixed, divide into 8 patties and shape into over-shaped patties. Dredge in flour and set aside.

Heat the olive oil over medium-high heat. Brown the patties, a few at a time, for just a minute on each side. Transfer to slow cooker, stacking if you need to.

In another mixing bowl, whisk together mushroom soup, au jus mix, and water. Pour over the patties in the slow cooker.

Cook on low for 6 hours or high for 4 hours.