Cross-post from my blog, domestic efforts:
Since my last post about veggie stock, I've perfected my technique quite a bit. Although I never make it quite the same way twice, I do follow a few consistent steps: I always slightly brown my base vegetables (onions, celery, and carrots), and I always add herbs and spices (see my suggestion in #3 below).
My directions are for a (preferably large) pressure cooker (which, imho, makes all the difference). I actually use a pressure canner since it's huge and can handle a lot of stock. If you don't have one, just simmer all of your ingredients in a large stock pot for about 45 minutes to an hour.
It's a good idea to start saving your vegetable scraps in a freezer bag. My freezer bag tends to include scraps of leeks, onions, random herbs, sweet peppers, and mushrooms. Once the freezer bag is full, I start a new batch of stock.
Rich and Deep Vegetable Stock
yields up to 10 pints, depending on how many vegetables you use
1. Coarsely chop 1 onion, 3-4 carrots, 3-4 celery stalks, and 1 leek (the last is optional, but oh-so-yummy). In a large pressure cooker or pressure canner, saute the veggies over 2 TBS of olive oil for about 5 minutes or until some have lightly browned.
2. If you've been saving veggies in a freezer bag, dump them in now. If you haven't, add coarsely chopped vegetables of your choice (but avoid brasiccas or add only tiny amounts). I typically add a handful of mushrooms, a sweet pepper, a handful of chives and/or green onions, and a tomato (either fresh, if in season, or canned).
3. Add water just to cover the whole lot. Then throw in 4-5 whole peeled garlic cloves, a dash of soy sauce, about a tablespoon of nutritional yeast (a trick I learned from Deborah Madison), about 2 teaspoons of peppercorns, 2-3 dried bay leaves, and several sprigs of fresh herbs (I've used various combinations of thyme, parsley, oregano, rosemary, and sage).
4. Pressure cook for 20 minutes.
5. Pour the stock through a strainer. Allow the stock to cool completely and pour into freezer-safe containers (I use wide-mouth Mason jars), leaving some headspace for expansion.
6. Freeze the stock.
7. You can discard (or compost!) the vegetables, although sometimes I puree them and throw them into a soup or stew recipe. My mom taught me this trick, and it works well for a number of soups. Plus, you don't waste the veggies that way.
8. Thaw stock as needed for recipe, and eat your heart out.