Mushrooms are packed with nutritional value. They’re low in calories, are great sources of fiber and protein (good for plant-based diets). They also provide many important nutrients, including B vitamins, selenium, potassium, copper, and (particularly when exposed to the sun) vitamin D. Certainly worthy of its very own day. Join us for a sampling of stuffed mushrooms. mushroom soup. mushroom pizza, mushroom risotto. mushroom gravy and many more mushroom delights.