To prepare the burger steak, place the vegan ground, onion, breadcrumbs, garlic, egg replacer, broth powder or bouillon paste, garlic powder, onion powder, and pepper in a large bowl, mixing to combine thoroughly.
Using your hands, form the seasoned ground into 4-ounce patties. You should get about 6 patties in total. Place the formed patties onto a parchment paper lined plate and place in the refrigerator while you prepare the gravy.
For the gravy, heat the oil in a saucepan over medium heat. Once the oil is hot, add the mushrooms and season with the salt and pepper. Cook, stirring every so often, until most of the moisture cooks out of the mushrooms and they’re lightly caramelized, 6 to 8 minutes. Transfer the mushrooms to a plate and set aside.
Place the vegan butter into the same saucepan over medium high heat. Once the butter is melted, sprinkle in the flour and whisk until a paste forms. Continue to cook, while whisking, until the paste turns light golden brown, 2 to 3 minutes. Slowly whisk in the broth until full incorporated. Add the reserved mushrooms back into the saucepan, reduce the heat to medium low and simmer, stirring ever few minutes, until the gravy thickens and reduces by about a third, 12 to 15 minutes.
Meanwhile, heat 1 tablespoon of oil in a large nonstick skillet over medium heat. Once the oil is hot, cook the burger steak patties until heated through and crisp around the edges, 4 to 6 minutes per side.
Serve with mushroom gravy, a side of rice or mashed potatoes, and enjoy!