Pistol River Portobello MushroomsPistol River Portobello Mushrooms These mushrooms are commercially grown in the USA. They are basically a brown button mushroom (Crimini) grown to a large size. They have a medium to strong flavor and are a great all purpose mushroom. Use them in any dish you want a mushroom flavor such as soups, sauces, gravies ect. Add them to a can of cream of mushroom soup, and you will not believe the flavor.