Roast Gammon with Blackened Crackling with Citrus, Rum and Raisin Sauce

As soon as you buy the gammon, remove all the wrapping and dry the skin really well with kitchen paper.

After that, using a very sharp, pointed knife, score the skin in a criss-cross pattern making little ½ inch (1 cm) diamonds. This is quite easy to do if you insert the tip of the knife only, then holding the skin taut with one hand, drag the tip of the knife down in long movements.

When you've done this, place the gammon on a plate and store uncovered on the bottom of the fridge, if possible for 2 or 3 days before you need it. This means the skin will go on drying, which makes better crackling. You can make the sauce well in advance, too. All you do is remove the outer zest from the orange using a potato peeler so that you don't get any of the pith. Then pile the little strips on top of one another and, using a very sharp knife, cut them into really thin needle-sized strips. If you've got the orange peel piled up, and your knife is sharp, this is a lot easier than it sounds. Next remove the zest from the lime, this time using a fine grater, and squeeze the juice from the lime and orange.

Place all the sauce ingredients, except the arrowroot, into a saucepan. Whisk the arrowroot into the mixture and place the pan on to a gentle heat, whisking all the time until it starts to simmer. As soon as this happens the sauce will change from opaque to clear, so then remove it from the heat and as soon as it is cool enough, pour it into a serving dish, cover with clingfilm and chill until needed.

To cook the gammon, pre-heat the oven to gas mark 9, 475°F (240°C). If the treacle is very cold, warm it slightly, then using a pastry brush, or a wodge of kitchen paper, lightly coat all the little diamonds of skin. After that sprinkle the skin with salt crystals, pressing them well in. Now place the gammon in a roasting tin, skin-side upright (if it won't stand up straight, use a couple of wedges of foil to keep it in position). Now place the roasting tin in the oven, and after 25 minutes turn the heat down to gas mark 4, 350°F (180°C). Then continue to let the gammon cook for 1¾-2 hours – it should feel tender all the way through when tested with a skewer.

After it comes out of the oven, give it at least 30 minutes' resting time, covered with foil, in a warm place. Remove the sauce from the fridge and serve the gammon carved in slices, giving each person some crackling, with some sauce spooned over.