Cut the oyster mushrooms and oyster shell mushrooms into bite-sized pieces.
Slice the onion and green onion.
Add cooking oil to a pan and stir-fry the green onion to make green onion oil.
Add the onion and stir-fry.
Add the oyster mushrooms and oyster shell mushrooms, and stir-fry on high heat.
Season with salt and pepper.
Transfer the finished mushroom stir-fry to a plate.