This recipe uses 8 cups of mushrooms, all cooked at once in a large cast-iron skillet. If you just really love mushrooms or if you're cooking for more than 4 people, you can do it but with this word of caution--crowding mushrooms in a pan will lead to them steaming, rather than cooking as intended. Because they're better freshly roasted, the best way to increase the amount is to cook 2 batches at once in separate pans.