To be used in soups as well as a broth added to grain dishes and whatnot. You'll definitely need to add salt when using it later, since none is added here.
Make sure all the vegetables have been cleaned of dirt.
2 medium potatoes, thickly chopped
2 white or yellow onions, skins removed and quartered
2 leeks, chopped into 0.5 inch pieces; remove the very root ends, but include the green tops
3 - 4 medium carrots (unpeeled), thickly chopped
3 - 5 garlic cloves, peeled and cut in half
couple handfulls of (unchopped) chervil and/or parsley (don't use cilantro, however!)
9 - 12 black peppercorns
1 - 2 bay leaves (depending on freshness), crumbled
1 apple or pear, quartered
1 sweet potato [optional --this adds more sweetness]
3.5 quarts water (use bottled or filtered water, if possible)
Put the peppercorns, chervil (and/or parsley) and bay leaves into a 8 - 10 quart pot. Putting the lighter items on the bottom will reduce their chances of floating up to the top when cooking.
Put in the rest of the ingredients.
Pour in the water.
Cover and carefully bring to a boil. Then set the heat to the lowest possible setting so that it continues to simmer. Simmer for about 45 minutes. Scrape off and dispose of any scum that rises to the surface.
Put a sieve that has four layers of cheesecloth into a dish from which you can easily pour, or into the ultimate storage container (the latter should be able to tolerate both hot and cold temps).
Ladle as much of liquid into the sieve. Transfer liquid to another container as necessary.
Ladle as much of the solid veggie matter+liquid that can be covered by the cheesecloth. The idea is to then grasp the ends of the cloth together over the veggies and squeeze as much liquid out as possible. Dispose of the cloth and veggies (put the latter in the compost :-).
Repeat (5) through (7) as needed (don't reuse the cheesecloth, tho').
You should get about 3 - 3.5 quarts of stock. It'll stay fine in the fridge for about 3 - 5 days. Freezes, well, indefinitely...