New ready made parmesan stuffed mushrooms. To cook, heat your oven to 180°c and line a shallow baking tray with baking paper or cooking spray. Place the mushrooms onto the tray and spread out evenly. Transfer to the oven and cook for 15-20 mins or until the cheese filling is cooked through and nicely golden. These mushrooms eat well by themselves or with a grilled steak or chicken and leafy salad.