Add the first seven ingredients into a large bowl and mix to combine. Divide the meat mixture into 6 even portions and shape each portion into an oval, each being approximately ½" thickness. Set aside.
Add the oil to a large skillet and heat over medium/high heat until the oil shimmers. Carefully add the patties into the skillet and sear them on both sides until brown. This will take about 2 minutes per side, and you may need to work in batches depending on the size of your skillet. Once browned, remove the patties to a plate and keep warm.
In the same skillet over medium/high heat, add the butter, remaining oil, and the prepared mushrooms to the skillet.
Cook the mushrooms, stirring occasionally, while scraping up the browned bits stuck to the bottom of the skillet from browning the beef patties. Cook for 3-4 minutes minutes, stirring occasionally until the mushrooms reduce in volume and caramelize in color.
Stir the flour and remaining salt into the skillet with the mushrooms, and cook, stirring frequently, for 1-2 minutes to remove the raw flavor from the flour.
Reduce the heat under the skillet to medium and stir in the beef stock and red wine. Continue cooking and stirring until the gravy thickens. This will take 2-3 minutes.
Once the gravy has thickened, nestle the beef patties back into the skillet and spoon the mushroom gravy over the top of the patties and cook for an additional 2-3 minutes or until the beef patties are heated through.
Serve the Salisbury steak over mashed potatoes or noodles and spoon the red wine and mushroom gravy liberally over top. Enjoy!
Video
Notes
Store any leftovers in an airtight container in the refrigerator for up to 5 days.May be frozen. Cool completely and store in an airtight freezer container or bag for up to 3 months. Thaw in the refrigerator overnight and reheat in a skillet with the red wine and mushroom gravy over medium heat until hot.