Start by placing ground beef in a bowl and seasoning it with salt, pepper, and a splash of Worcestershire sauce. Mix gently, then shape the mixture into thick oval patties.
Heat a pan over medium-high heat and sear the patties until nicely browned on both sides. Once done, remove them from the pan and set aside.
In the same pan, add sliced onions and cook until soft and fragrant. Stir in a little flour, then slowly pour in beef broth while mixing, allowing the sauce to simmer until it becomes rich and smooth.
Return the patties to the pan and let them cook gently in the gravy until tender and fully infused with flavor.
Meanwhile, prepare the mashed potatoes by boiling them until soft, then mashing with butter and a splash of milk until creamy and smooth.
To serve, place a generous portion of mashed potatoes on a plate, top with the Salisbury steak, and spoon plenty of the thick, savory gravy over everything. Cut into one patty and enjoy as the juices blend perfectly with the creamy mash.