Once the gammon has baked for its two hours, remove the dish from the oven and take off the foil. Turn the oven back to 400 F / 200 C — ready for your glazed gammon.
Now use a large sieve to drain off — and keep — all the juices from the baking dish. That should give you about 1 ½ cups of those very important juices — remember, they’re the flavor-packed stock for your cranberry sauce. The veg has now done its job and can be discarded.
Set the gammon on a plate, and let it cool for about ten minutes — so it’s cool enough for you to cut away the netting.
Once the netting’s removed, it’s time to peel off the gammon’s rind. So, in one corner of the rind, use a sharp knife to make a small cut between the rind and the fat beneath it. Make the cut as close to the underside of the rind as you can. You’re aiming to make a small, corner flap of rind that you can easily grip, and then gently pull the whole rind away from its underlying layer of fat.
Use a sharp knife to make a series of criss-cross cuts right through the layer of fat. Only cut through the fat, and not into the meat below. I do this in two stages — making parallel cuts in one direction, followed by a second set of cuts at right-angles to the first. Space the cuts about 1/3 inch apart so that you create a diamond pattern all over the fat.
Set the patterned gammon back into the now-empty baking dish, and spoon your glaze all over the top and sides of the gammon.
You want as much glaze as possible to fill your diamond-pattern cuts, but take care not to break that pattern apart as you spoon in the glaze. Some glaze will likely run off the sides, that’s fine — leave it where it settles around the gammon — just get as much glaze as you can onto the gammon.
Return the glazed gammon to a high shelf in your 400 F / 200 C oven, and let it bake there — uncovered — for about 30 minutes. After 15 minutes, baste the gammon thoroughly with the glaze from the bottom of its baking dish.
You’re aiming for the glaze to darken and start to form a sticky, softish crust on the gammon. It might take a little longer than 30 minutes for that to happen, so let the gammon bake for another 5 minutes or so until it does. But, bear in mind that you’re not looking for a crisped crust, just one that’s softish and sticky. Good — your gammon’s done. And so are the sweet potatoes.
So, turn off the oven, and transfer the gammon to a carving board — ready for being carved in about ten minutes. The bubbling sweet potatoes can stay in the cooling oven until you’re ready to serve them.