The effects of the curing process that I use in this recipe is not easy to understand. In fact it is highly counter-intuitive. The meat ends up MORE moist and tender, even thought the cure draws out water and firms up the meat.
The reason for this is that as the chloride ions from the salt penetrate the meat, it causes a change to the proteins in the meat that bind the water to the flesh more tightly, and resists the shrinking of muscle fibres that would force water out when cooking. For more information on this, see Modernist Cuisine, vol 3, p154
In theory, brining meat in a solution of salt and sugar should be even more moist than the dry-rub curing I use in this recipe, as the dry rub draws water out by osmosis, whereas the brine would not. However, I cannot support this theory – testing out two pieces of pork cut from the same belly, one dry cured similarly to above and one brined, I found the dry cure tastier and more succulent.
The role of sugar in the cure to balance the taste of the salt. Much as with the brining issue, I can find no support in books I read for a cure with as high a ratio of sugar to salt as I use here (2 parts sugar to 1 part salt). Modernist Cuisine, for instance, has their SWEET dry rub at a 1:2 ratio – twice as much salt as sugar, 4 times as salty as my cure. That’s the ratio I use for my SALTY cure (when I make bacon, for instance). As I say, I cannot account for the dramatic divergence between my use of sugar and what is used by apparently everyone else – I can only assure you that it’s not a typo: twice as much sugar as salt is my recipe, and I have tested a range of cures to find the best one for this purpose.
Although I call it “slow roast”, the proper term for this dish would be “pot-roast” or “braised”. Although it’s simple to put meat, liquid and possibly some vegetables in a pot, put a lid on it, and leave it alone for a few hours, from a scientific point of view, a pot-roast is remarkably complex. It uses convention, conduction, radiation, as well as both wet and dry heat.
The liquid keeps the meat and the air around the meat moist. It also (and more importantly) it keeps the food from scorching by quenching any hot spots that occur on the base of the pot. This does not require a lot of liquid, and it’s better not to use more than required – if you use too much, the meat will boil rather than braise, and will lose it’s flavour into the liquid. Some flavour does of course go into the liquid, making it into a sauce that you can serve with the meat or reserve for use in another dish.
Covering the pot with a tight-fitting lid has a number of effects. Radiant heat from the lid causes the meat to brown (Malliard reactions), which creates great flavour. The lid also stops those flavours from escaping into the air. And by trapping the moisture in the pot, the meat cooks more quickly (because moist air conducts head better than dry air – “it’s not the heat it’s the humidity”) and dries out less because evaporation is reduced by the air already being full of moisture. For these reasons, if you don’t have a lid and have to resort to a foil cover, try to get the tightest fit you can with it.
Skimming a sauce is to remove the oil/fat from the water-based portion of the sauce. Because oil and water don’t mix and the latter is more dense, the oil will “float” on top of the water, if you leave the sauce to settle for a minute. You can “skim” this off with a spoon by dipping it carefully into the oily layer and scooping it out one spoonful at a time (if you do so, you may find it easier to use a less wide container for the liquid as this will increase the depth of the oil layer).
However, a much easier and more effective way is to put the sauce in a pint glass or a pyrex measuring jug and put it in the fridge (glass will allow you to see the two layers clearly). As it cools to fridge temperature, the fat in the sauce will set solid at the top and can be scooped out. If there is enough gelatin in the water-based layer, it may also set solid.
I recommend not using the skin of the pork for this recipe. It’s not really possible to get a satisfying crackling to come up, so the skin will either be rubbery and flacid or hard and leathery. You can ask your butcher to remove it, or you can take it off yourself with a sharp knife while raw, which is not very hard but does requires some patience. This allows you to use the skin for another recipe (like pork rinds, or to enrich a stock/stew). Alternatively, if you’re short on time and did not have the butcher remove it, you can cook the pork up to right before the glazing stage, and remove the skin easily from the tender meat at this point.
Pork belly often comes with the belly ribs in. If you wish, you can bone out the ribs/have your butcher do it for you. Then you have a rack of ribs which you can cook any way you like. Personally though, I tend to leave the ribs in when I cook the pork, and cut them off at the end of the cooking time (the meat is very tender so this is easy). The ribs are a chefs treat – ugly, but delicious. There is a certain amount of cartilage to watch out for though, which you CAN eat, but it has an al dente kind of mouthfeel that I personally find quite unpleasant.
As with most pork recipes, if you like fennel or aniseed-y flavours, add some fennel seeds or star anise to the rub or to the glaze. Please don’t make me eat it though – I can’t stand the taste of aniseed.