Although suitable as a main I often use this as a side dish. The three types of mushrooms, pioppino, black and straw, are stir fried with tofu then joined by oyster sauce.
Pioppino are a type of Japanese mushroom. They are also known as black poplar mushrooms and shimeji.
Black fungus are also known as wood ear mushrooms.
You will find both types of mushrooms in Asian speciality shops.
If you like a thicker sauce add a little bit of cornflour and water to the sauce towards the end.