Combine all of the ingredients for the Salisbury steaks in a bowl and mix well forming into 4 evenly sized patties.
In a medium sized pan, melt the butter and then add the diced onion.
Cook for 2-3 minutes then add the flour and the Worcester sauce and soy sauce mixing well.
Gradually add the beef stock and bring to a simmer cooking over a low heat for about 5 minutes and the gravy becomes thicker.
Season with salt and pepper and keep over the lowest heat while you cook the beef patties.
In another non stick pan add a splash of olive oil over a medium heat.
Place each beef patty into the hot oil and cook for about 3-4 minutes before flipping them over and repeating on the other side until fully cooked.
Place the desired amount of patties on a plate with mashed potatoes and spoon over some of the brown gravy on top.