In a medium bowl mix together with your hands all of the ingredients for the beef patties (hamburger, bread crumbs, egg, garlic, salt & pepper).
Form hamburger mixture into 6 uniformly shaped patties about 1/2 inch thick.
In a large non-stick skillet brown patties on medium-high heat for about 2 - 3 minutes on each side.
Gently transfer browned ground beef patties to the bottom of a 3.5 quart casserole slow cooker OR a 6 quart or larger slow cooker.
Mushroom & Onion Gravy
Place sliced mushrooms and sliced onions over the top of the beef patties in the slow cooker.
In a small bowl mix together the rest of the gravy ingredients (onion soup mix, flour, beef stock, parsley and balasmic glaze if using). Whisk together until the flour is dissolved in the liquid.
Pour gravy mixture over beef patties, onion and mushrooms in the slow cooker.
Cover and cook on LOW for 5 to 6 hours.
Serve patties and gravy over mashed potatoes, cooked rice or egg noodles. Sprinkle with additional chopped fresh parsley for a bright pop of color!
Notes
Turn this recipe into an appetizer! Instead of forming the ground beef mixture into 6 patties, roll it into about 30 meatballs. Brown the meatballs briefly in a frying pan and following the rest of the recipe directions for delicious little Salisbury meatballs made in your slow cooker! Nutritional information based on beef patties and mushroom gravy and does not include rice, noodles or potatoes that you may serve it with.