Onions, Carrots, Celery, Leeks, Parsnips, Fresh Thyme, Fresh Parsley, and Mushrooms give the best stock recipe, but you can add any vegetable of your choice. I have used dried mushrooms in this recipe as they give a very earthy taste to the stock. But you can choose to skip them and use fresh mushrooms if dried ones are not available. Just make sure you avoid the vegetables mentioned below to not use in stock so that your stock doesn't taste bitter or turn very dark in color.