Update: check out my new Yorkshire Pudding recipe/method/analysis here
Roast pork without good crackling is like a garden without any trees, a car without hub-caps, a jester without any bells, a farm without any dung, or a young vagabond without a twinkle in his rapscallious eye. It is missing its joy. There is something about the crisp, salty, melt-in-your mouth goodness of crackling that brings joy to the iciest of hearts.
People always seem to want to know how to get a good crackle, and there are a few common advices offered by various chefs and food writers. They variously suggest rubbing with oil, rubbing with salt, with herbs, scalding with boiling water, scoring and so on. But I have never seen any writer offer an explanation of why pigskin crackles, and how any of the standard methods actually help.
This post is my explanation of the processes involved in making crackling. As with the vast majority of culinary methods of which I know, if you just follow instructions and recipes without really thinking about what is actually happening to the ingredients then you will have little success.
It is perfectly possible to employ all the methods mentioned above and not get a good crackling. If you have found yourself frequently frustrated, left with a tough leathery bit of football I would suggest that you try the following: run a blow torch over it. Voila! It will sizzle and puff up into light crisp balloons of crackling. It is not the best, mind you: it will be patchy and uneven. But the blowtorch just illustrates that there is no magic involved. It is heat that is the critical factor.
Think of bacon turning crispy. When you fry or grill it for long enough, it will go as crunchy as a poppadum. Water is driven out, and fat soaks in, cooking the pork cells brittle. Blowtorching the skin is essentially doing the same thing as frying bacon. There is fat underneath which melts and cooks the skin, replacing the water which is driven out.
When moisture is trapped in or under the skin, fat can not usurp its place. Scoring the rind allows the moisture to escape and the fat to melt out and all over the skin, just like bacon in a frying pan. As sharp a blade as possible, even a scalpel is good. But don’t cut all the way down through the fat to the flesh, because this can allow juices to bubble out, ruining the meat and the crackling.
I have seen one well-known chef recommend pouring boiling water over the skin before oiling, salting, and cooking. This will not help. I imagine that the chef borrowed the step from traditional Peking duck preparation, where the skin is scalded first to tighten it and to remove any fat on the surface of the skin. This is important because the ducks are left to hang in a draughty window or doorway (Chinatown stylee) for a day to completely desiccate the skin, and residual oil would prevent the water leaving it. Chinese chefs take care not to pierce the skin so no fat can get through and spoil it. When Peking duck is done in authentic Beijing style, the skin is served first with pancakes – it is a fine delicacy. The rest of the duck meat is dished up in a subsequent course.
Anyway, the scalding is pretty much useless in the above chef’s recipe because the pork joint is not left to dry for any length of time, and oil is poured straight back on to the skin!
Salting- it seems like a good idea. Salting things dries them out, of course. Well, salting dries out food without having to cook it, more specifically. If the water is free to escape, then the heat from the cooking will be far more effective at drying the skin than salting. However, the mixture of excessive fat and salt is a combination you are genetically predisposed to adore. Great for your heart, too.
Heat is everything. If you keep the oven low you will not get crackling. If you turn it up very hot then you run the risk of drying your perfectly juicy pork (and there is no greater sin than dried-out pork, not even usury). Pork does not like to be cooked roughly. It makes sense to remove the rind, fat and skin, when the joint has finished cooking and put it back in a very hot oven You can even use the grill. Incidentally, I always wrap roasted meat in foil to rest. If you merely cover it, it will lose a lot more juice and juiciness. If grilling the crackling, take care not to let it burn, all can be lost in a matter of seconds (this nearly happened to me the other day).
Last but not least we come to the cut of meat itself. A good layer of fat really helps get the crackling sizzling, and also show that the pig has been fed well. You should only use good quality, free-range pork. Factory-farmed pork always has a terrible, unwholesome reek to it, and sweats all sorts of weird muck. I found out from a farmer that this curdled grey crap is actually milk: there are government regulations governing how much water may be pumped into standard non free-range meat, so the factory technicians use milk as well, which has not been regulated yet.
So, if you want a vague recipe, score the skin shallowly (experiment with using a lot of scores) rub in some salt for flavouring. Use a high heat (above 220C) to crackle the pork, preferably off the joint after cooking. Oil may help to keep salt on, and make up for a lack of fat, but if there is enough blubber underneath the skin then that should do.
But the only way to get reliably good crackling is to experiment, trying to get a feel for the cooking process. Every oven and every piece of pork is different, and your method will have to adapt accordingly.