Combine ground ham, crushed crackers, egg and barbecue sauce and shape into 6 patties. In a skillet, saute potato and onion slices in butter and oil over medium heat, turning frequently to prevent browning. Drain and place in crockpot. Combine milk, cheese and seasonings and pour over potatoes and onions. Layer ham patties on top. Cover and cook on Low for 3 to 5 hours. Serves 6