Line a rimmed baking sheet with foil and then rub with a teaspoon of avocado oil to prevent sticking. Lay the steak on top and season all over with 1 tablespoon of the soy sauce.

Broil on high in a preheated broiler for 3-4 minutes per side. Remove from oven and allow the steaks to rest for 10 minutes before slicing against the grain.

While the steak cooks, prepare the sauce. Heat a large pan over high heat and add the remaining teaspoon avocado oil. Add the onions and cook until softened and beginning to brown. Add a bit of chicken stock if they begin to darken too quickly or burn. Add the garlic and cook until fragrant, one minute more.

Add the mushrooms and remaining tablespoon soy sauce. The mushrooms will release liquid as they cook. Cook on high heat until they have released their liquid and there is little to no liquid remaining. Add the chicken stock and gelatin and boil until the sauce is reduced to a couple of tablespoons. Season to taste with salt and pepper and set aside.

Slice the steak and transfer to serving plates. Spoon the mushrooms over top and sprinkle with parsley.