In a large bowl, combine the ground beef, bread crumbs, egg, milk, finely chopped onion, minced garlic, Worcestershire sauce, Dijon mustard, salt, and pepper. Mix gently until just combined; avoid overmixing to keep the patties tender. Divide the mixture into 4 equal portions and shape them into oval patties, about 1/2 inch thick.

Heat the olive oil in a large skillet over medium-high heat. Add the patties and cook for 4-5 minutes per side until they are nicely browned. Remove the patties from the skillet and set them aside.

Using the same skillet, add the butter and thinly sliced onions. Cook over medium heat for about 8-10 minutes, stirring occasionally, until the onions are softened and beautifully caramelized.

Sprinkle the flour over the onions and stir it in. Cook this mixture (the roux) for 1-2 minutes to cook out the raw flour taste.

Gradually whisk the beef broth into the roux, making sure to eliminate any lumps. Stir in the Worcestershire sauce and Dijon mustard. Bring the gravy to a simmer, stirring constantly until it thickens to your desired consistency.

Return the seared patties to the skillet, nesting them into the gravy. Reduce the heat to low, cover the skillet, and let the Salisbury steaks simmer in the gravy for approximately 10 minutes, or until they are fully cooked through.

Taste the gravy and adjust the seasoning with salt and pepper as needed. Serve the Salisbury steaks hot, generously topped with the gravy. They pair well with mashed potatoes, rice, or steamed vegetables.Tips for Success