The straw mushroom (Volvariella volvacea) is a small, egg-shaped tropical mushroom and one of the most heavily cultivated edible fungi in the world, grown on beds of rice straw across the hot, humid lowlands of East and Southeast Asia. Harvested young, while still enclosed in a papery outer veil (the volva), it looks like a smooth grey-brown to blackish "egg"; sliced open it reveals the pale cap and stem folded inside. Mild, faintly earthy and pleasantly slippery-tender, it is a workhorse of Chinese, Thai, Vietnamese and Filipino cooking — the familiar sliced button in canned "straw mushrooms" that turns up worldwide in stir-fries, hot-and-sour soup, tom yam and countless braises.