1Start by grating half of an onion into a mixing bowl.
2Add half a cup of panko breadcrumbs to the grated onion.
3Using your fingers, mix the breadcrumbs and onion together and let the breadcrumbs soak in the onion juices for about five minutes.
4Add one pound of ground beef, one whole egg, three tablespoons of Dijon mustard, two tablespoons of ketchup, and half a teaspoon of Worcestershire sauce.
5Add one or two minced garlic cloves and one beef bouillon cube, breaking it up and sprinkling it in.
6Use hand mixers to mix all the ingredients until beautifully combined.
7Form the mixture into five patties.
8Place the patties on a hot oiled pan and sear them well on both sides.
9Remove the seared patties from the pan and set them aside on a plate.
10Add the other half of the onion, diced, and two more minced garlic cloves to the pan. Sauté until they look beautiful.
11Add two cups of sliced mushrooms to the pan and continue sautéing.
12Once the mushrooms are done sautéing, add two tablespoons of butter and three tablespoons of flour to the pan.
13Mix the butter and flour together, cook it off to make a roux.
14Slowly pour in two cups of beef broth, mixing constantly until all lumps are gone and deglaze the pan.
15Add two teaspoons of Worcestershire sauce, a little bit of salt, and a little bit of pepper.
16Stir everything in and bring the sauce to a simmer.
17Return the patties to the pan, placing them in the simmering sauce.
18Let the patties simmer in the sauce until the sauce thickens and the patties are cooked through.
19Serve the Salisbury steak with mushrooms and gravy over mashed potatoes.