Add the Panko breadcrumbs to a large bowl. Add the finely diced onion to the breadcrumbs and mix the two together with a rubber spatula until combined. Let these two sit together for a few minutes for the breadcrumbs to absorb the onion juices.

Add in the rest of the steak ingredients into the bowl with the onions and breadcrumbs. Combine all with your hands without over mixing the mixture.

Form the beef mixture into 5-6 round steak patties.

Heat oil in a large skillet over high heat. Add the steaks into the pan. Brown and cook for one minute on each side (they will still be raw on the inside). Move the steaks out of the pan onto a plate. Make the mushroom gravy.

Add a little more olive oil to the hot pan if needed.

Add diced onion and sauté for 2 minutes until the onions are translucent.

Add the butter and the mushrooms into the skillet and cook for 2 - 3 minutes until the mushrooms are browned.

Sprinkle in the flour, stir and cook the flour for 30 seconds, stirring constantly.

Slowly add in the beef broth, stirring to combine to make sure there are no lumps.Once mostly lump free, whisk in the rest of the gravy ingredients.

Add the steaks back into the pan with the mushroom gravy along with any juices on the plate. Cook for 5 - 7 minutes more. The gravy will thicken while you stir occasionally around the steaks. If the gravy thickens too much, you can always add in more beef broth.

Season the gravy with more salt and pepper if desired.

Serve Salisbury Steaks and gravy over creamy mashed potatoes.