Step 1: Prepare the Patties

1. In a large mixing bowl, combine the ground beef, breadcrumbs, egg, milk, chopped onion, minced garlic, Dijon mustard, Worcestershire sauce, smoked paprika, salt, and black pepper. Mix gently with your hands until just combined. Overmixing can make the patties tough.
2. Divide the mixture into four equal portions and shape into oval-shaped patties about ¾-inch thick. Set aside.

Step 2: Sear the Patties

1. Heat a large skillet over medium-high heat and add a drizzle of olive oil. Once hot, add the patties in a single layer.
2. Cook for 3–4 minutes per side until browned but not fully cooked through. Remove the patties from the skillet and set aside. They will finish cooking in the gravy.

Step 3: Prepare the Gravy

1. In the same skillet, reduce the heat to medium and add the butter and olive oil. Once melted, add the sliced onions and cook for 3–4 minutes until softened.
2. Add the mushrooms and continue cooking until they release their liquid and become golden brown, about 5–6 minutes.
3. Stir in the minced garlic and cook for 30 seconds until fragrant.
4. Sprinkle the flour over the onion and mushroom mixture, stirring well to coat. Cook for 1–2 minutes to remove the raw flour taste.
5. Gradually pour in the beef stock while whisking to avoid lumps. Add the Worcestershire sauce, Dijon mustard, salt, and pepper. Bring the mixture to a gentle simmer.

Step 4: Combine the Patties and Gravy

1. Return the seared patties to the skillet, nestling them into the gravy.
2. Cover the skillet and let the patties simmer in the gravy for 15–20 minutes, or until they are fully cooked and the gravy has thickened.
3. Taste the gravy and adjust the seasoning with additional salt and pepper, if needed.

Step 5: Serve

1. Serve the Salisbury steak patties hot, generously spooned with the mushroom gravy. Garnish with fresh parsley for a pop of color and flavor.
2. Pair with mashed potatoes, rice, or egg noodles for the ultimate comfort meal.