Enoki mushrooms are thin, white and long. They are very healthy and full of antioxidants. This is a very common dish in Hong Kong. The black pepper sauce is the key of this dish. Since the beef and mushroom has no season, the black pepper sauce keep the beef moist and flavorful. The only problem is buying thinly sliced rib-eye beef. I bought them in Chinese supermarket. But if you can’t go to Chinese supermarket, you can probably ask your local butcher to slice your rib-eye thin.