1 10 3/4-ounce can condensed cream of mushroom soup
1 cup water
1/2 teaspoon beef bouillon granules or beef base, or to taste, optional
1/2 to 1 teaspoon gravy browning sauce, such as Gravy Master, optional
Instructions
In a bowl, combine the mustard, Worcestershire sauce, egg, bread crumbs, milk, and salt. Whisk to blend. Add the ground beef and finely chopped onion; knead to blend ingredients.
Shape the beef mixture into 4 large patties or 5 to 6 small patties.
Heat butter in a large skillet over medium heat. Saute the mushrooms, stirring frequently, until tender and browned. Remove the mushrooms to a plate and set aside.
Add 2 tablespoons of vegetable oil to the skillet. Brown the patties on one side; turn carefully to brown the other side.
Meanwhile, combine the soup with the water and optional beef bouillon and gravy browning sauce; stir in the mushrooms. Pour the mushroom sauce mixture over the Salisbury steaks. Reduce heat to low, cover, and simmer for about 10 minutes, or until the meat is cooked through.