2 large onions (don’t bother to peel), cut in half
4 large carrots (don’t bother to peel), cut into large pieces
4 large celery stalks, cut into large pieces
1 large potato, cut into chunks
6 garlic cloves (don’t bother to peel)
15 button mushrooms
2 large tomatoes, roughly chopped (or use one 28-ounce can; don’t bother to drain)
2 bay leaves
6 sprigs fresh parsley, optional
Salt and freshly ground black pepper
Instructions
Put the soy sauce and all of the vegetables, the bay leaves, and the parsley if you’re using it in a stockpot with a good sprinkle of salt and pepper. Add 1 gallon (16 cups) water and turn the heat to high. Bring just to a boil and then lower the heat so that the mixture bubbles steadily. Cook, undisturbed, until the all the vegetables are very tender, at least 30 minutes. To develop more intense flavors, let the stock cook for up to 2 hours; check on it once in a while to make sure it’s still bubbling gently.
When the stock is done, turn off the heat and let it cool slightly, then put a strainer or colander over a large pot and carefully pour in the stock; press down on the vegetables to extract as much liquid as possible from them. Sprinkle the stock with a little salt and pepper and discard the vegetables. Use the stock immediately or refrigerate it for up to 5 days or freeze it for up to 3 months.