Chop the onion thin and make the garlic into a pure. Put some sesame oil in a large pan and when hot add the onion and e garlic and cook until soft. Keep the marinade or if you don’t have any left make a little bit more. Add the mushrooms and lay them flat don’t let them touch each other turn them exactly as you would with a steak but cook it for about 3’ on each side. You might need to do batches if you don’t have a pan big enough.