Rinse the ham hock in water, then place it in a large pan and add water to cover. Add the onion halves, whole carrot, garlic halves, parsley stalks, thyme sprigs, bay leaves and peppercorns, and place the pan on a medium–high heat. As the contents of the pan come up to the boil, turn down the heat to a simmer and skim away any froth that rises to the surface. Simmer, uncovered, for 3 hours, or until the meat is tender and comes away from the bone with ease.

Heat the oven to 180°C/350°F/gas mark 4. Lift the hock into a small roasting tray, reserving the stock. When the meat is cool enough to handle, peel away the soft skin and place it underneath the meat. Combine the sugar and mustard, then spoon the mixture over the meat. Scatter over the sage leaves, and roast in the oven for 25–30 minutes, until bubbling and caramelized. Remove from the oven and keep warm.

Meanwhile, pass the ham stock through a fine sieve into a bowl and set aside. Use the back of a spoon to push through as much flavour from the vegetables as possible. Bring 750–800ml
(26fl oz–28fl oz) of the stock up to a gentle simmer in a large, heavy-based pan. Pour in the polenta in a slow, steady stream, stirring well as you add it. It will thicken quite quickly, but will need gentle simmering for 6–8 minutes, until the grain is cooked properly. If it becomes too thick, add a dash more stock. Stir in the cheese, butter and chopped parsley, and season, if necessary.

Divide the polenta between four plates. Shred, tear and cut off chunks of ham and pile them onto the polenta. Spoon over any roasting juices and bring to the table straight away.