Portobello mushrooms are large, mature cremini mushrooms with a meaty texture and earthy flavor. They are often grilled, roasted, or stuffed, making them a popular vegetarian substitute for meat. Their wide, open caps and dark gills make them ideal for holding fillings or topping burgers. Nutritionally, they’re low in calories, rich in fiber, and a good source of antioxidants, vitamins, and minerals.