Case Size: 22/33.8 fl oz. A vegetarian alternative to oyster sauce, made from mushrooms to provide umami flavor. Wan Ja Shan Vegetarian Mushroom Oyster Sauce (1200 g) is a rich, plant-based alternative to traditional oyster sauce. It adds an umami-rich flavor to stir-fries, soups, and marinades, making it a versatile vegan option for many dishes.