Mix breadcrumbs, egg replacer, ketchup, Worchestershire sauce, mustard and salt together in a large bowl. The mixture should start to thicken.

Add each seitan loaf to the bowl and pat mixture onto them so that they’re covered on the outside.

Heat oil over medium heat in large skillet. Add the steaks and cook until slightly brown on each side. Remove and set aside.

Heat butter over low heat and add onions. Cook for two minutes and then add garlic. Cook for another minute and add mushrooms. Cook, stirring frequently, until they start to brown—about 3 minutes.

Add flour and stir until everything is coated. Stir in vegetable stock. Turn to high heat until gravy begins to boil and reduce to a simmer. Stir in salt and pepper.

Return steaks to skillet, cover and cook until gravy thickens, about 10 minutes.