In a large bowl, measure and combine the ground beef with the onion, eggs, bread crumbs, Worcestershire, milk, salt and pepper. Divide mixture into 8 even portions and form into oval patties.
In a large, deep skillet, heat 1 1/2 tablespoons olive oil over medium heat. Brown four patties evenly, about 4-5 minutes each side and remove. Add remaining 1 1/2 tablespoons olive oil and repeat browning the next four patties. Remove from pan and set aside.
In remaining pan juices, cook mushrooms until tender, about 3 minutes. Remove from pan. (If there isn't enough grease left, add in another tablespoon of olive oil.)
For the gravy, melt butter in same hot pan. Sprinkle in flour and whisk to create a paste. Cook one minute. Whisk in beef consommé and beef broth and bring to boil to thicken. Reduce heat to simmer and stir in Worcestershire sauce and dijon mustard. Taste and add salt and pepper as needed.
Add in mushrooms and cooked steaks. Coat in gravy, cover and cook on low until salisbury steaks are cooked completely through, 15 minutes or so. Serve hot with any desired side dishes.