I just blogged about making instant stock powder from things that are naturally savoury (and compact). But the best stock to me is still traditional bone broths, simmered over hours to extract not just flavour, but minerals and nutrients. Back home in Singapore, my mum makes stock almost everyday, slow-cooked in a huge black claypot over a charcoal fire, with a very precise selection of bones from specific parts of specific animals for the right flavour.
Here, I do things a lot simpler.
Stock is basically just bones, simmered in water, hence also called bone broth (of course, there's also the vegetable stock i.e. onions carrots celery leeks, in a pot, about an hour). There aren't really any hard and fast rules, but read on anyway. I've got tips, and I also want to bring up Chinese stocks, which are quite different in many ways!
My mum's big black stockpot over a charcoal fire
The bones and bits
You can use a leftover chicken carcass, or if you don't often buy a whole chicken because you're cooking for one, just save your bones from after you finish eating a drumstick or something. Bones that have been pre-roasted will give a "brown" stock, fresh bones will give a "white" stock. You'll also often find carcasses on sale at the farmers' market, or just ask your butcher for beef, or veal, bones, usually for free. In chinese cooking, pork bones are favoured. Yes, pig's tail. For really gelatinous broth, add chicken feet/wings/neck/pork trotters/ears/tail. For fish stock, fish heads are best.
To boil or not to boil?
The Sally Fallon method calls for the bones to sit in cold water with a tablespoon of vinegar added for an hour or so before bringing it up to a boil, to extract all the calcium and minerals.
For Chinese stock though, the first step is always to parboil the bones. That gets rid of most of the blood and impurities and makes for a cleaner, clearer stock. I prefer this, it gives a much better result, and I doubt there's much difference in the nutrient content after all those hours of simmering.
A bubbling pot of stock
Whether or not you parboil the bones at first, you want to bring the bones and water to a boil, and then immediately reduce to a simmer, over low heat, for the rest of the time. There should be just a tiny bit of bubbling action, think that minimal bubble stream you see from a goldfish in a tank. Keep skimming any scum that you see on top, though the parboiling step helps to reduce the amount of scum.
For how long?
The general attitude usually is, for as long as you can. Your aim is to extract everything out from the bones, flavour and nutrients-wise. I usually leave it overnight in the slow cooker on low, and the next day, the bones become useless and soft enough to crush with a spoon. But my mum says 3-4 hours or the colour of the stock gets affected. Only 1/2 hour for fish stock, as fish bones are quite delicate, and you only need a short while of bare simmering to extract its goodness.*
You can add nothing, or anything, really
I think next time I refer to stock in my recipes, I'll be slightly more specific and say 1, 2, or 3.
1. The Western stock usually calls for onions, carrots, celery, maybe leeks or bay leaf too. I save the carrot tops and base of celery etc and freeze them to add to stocks, or even to make vegetable stock. So, repeat, it can really cost nothing.
2. The Chinese stock calls for ginger and spring onions, which helps to get rid of the undesired "smell". Sometimes a dash of rice wine, for the same reason. I think it also works as a sort of acidic medium much like Sally Fallon's vinegar, to extract nutrients. Oh, and contrary to popular belief, no garlic.
3. You can add nothing at all too, which is what I like to do usually because I don't know if I'll be using it for what kind of recipes.
4. Just thought of this. Asians often don't just make basic stocks to add to dishes, often we just make soup with bones straight away, slow-simmered with various herbs/ingredients for different types of soups. An example is gamjatang, a Korean pork bone soup, and there's the many Chinese "long-fire soups" 老火汤.
So what is good stock?
Good stock should gel when refrigerated (see above/below). That's collagen that you can get much better than any collagen pill. Colour will differ based on type of stock.
In addition, if it's Chinese stock, chefs (and chinese mums) will look for stock clarity. To get that, you not only have to follow all the tips above for chinese stock, but you should ideally skim off the fat after chilling (DON'T THROW, save for cooking!) and use bones that are not fatty, because the fat globules dispersed in the stock makes it not as clear as it can be. My mum's specific blend for clear stock 清高汤 includes the bones from the back of the pig, chicken feet, chicken breast bone, and dried scallops. But she also makes stocks from pig's tail and trotters for other dishes, and I really love the rich taste of those stocks.
This soup is considered not clear enough.
That's one example of 老火汤- pork bones, with dried cuttlefish, daikon radish and goji berries. It's delicious, clear or not.
So, after all that, I just want to say, homemade stock is a wonderful and very important thing to do for our health and for our cooking, and it doesn't matter so much what is the 'right' way and whether you make it in the perfect way or not! I hope when we realise how simple (and cheap!) it is, we can all make it a point to start making our own stock instead of paying for that preservative-filled Knorr cube.
* See here for a different kind of fish stock, which is milky white, made by a furious emulsification of collagen and fat with stock!