Combine all steak ingredients in a large mixing bowl and mix well until all ingredients are thoroughly combined. Then divide meat mixture into quarters and roll into balls. Flatten them into ovals roughly the size of a ribeye steak about 3/4 inch thick. Press dimples into the top surfaces of the steaks (this will keep them flat as they cook rather than rounding up).

Heat a large cast iron pan over medium heat until hot, add a tablespoon of oil and when hot, add the steaks with the dimples facing up. Cook over medium heat until the first side is browned, 8-10 minutes then flip and cook another 8-10 minutes, or until cooked to your liking (145ºF). Remove steaks to a plate and rest them while you cook the sauce.

In the now empty pan, add the second tablespoon of oil and then add the mushrooms, cooking over medium high heat until they release liquid, stirring often until they brown, another 5 minutes or so. Add onion and continue to cook until they soften and begin to brown, another couple of minutes. Add tomato paste, and cook for another minute. Add stock and gelatin and bring to a boil, stirring occasionally until the sauce has reduced by half and thickened. Add Worcestershire sauce and season with salt and pepper then stir in butter, stirring well to incorporate. Taste and adjust seasoning with vinegar, salt, and pepper as desired.

Add back steaks and their juice, warming through and then serve with the sauce spooned over top.