At least 2½ hours before you want to serve: scrub the trotters well and remove any hairs over a gas flame or using a disposable razor. Brown the trotters all over in a little olive oil, add half of the onion, the carrot and the celery. Cover with chicken stock and braise for about 1½ hours, until the trotters are tender but not split.
Towards the end of the trotters’ cooking time, make the chicken mousse (as with making mayonnaise, it helps if all the ingredients and utensils – including the processor – are well chilled): in a blender or food processor, purée the chicken with the salt until smooth, about 3 seconds, then scrape the mixture down the sides and process for 15 seconds more to make sure no meat is left unprocessed.
Add the egg white and process for another 15 seconds, scrape down and add about 2tablespoons of the cream. Process for a further 10 seconds, then scrape down again.
With the machine running, slowly pour in the rest of the cream to produce a smooth mixture. This should take 20-30 seconds. Don’t take too long or the machine will heat the mixture up. In the professional kitchen this mixture would now be forced through a sieve, but you can use it just as it is; it won’t make much difference to the finished result.
When the trotters are braised, allow to cool slightly, then remove the flesh from the bone (see pages 130-31) and scrape the fat away.
On a flat work surface, roll out a 30-cm / 12inch-long piece of cling-film and place the trotters on it lengthwise.
Chop the remaining onion finely and boil until soft, about 1 minute. Refresh in cold water, then drain and pat dry. Mix into 200g / 7oz. of the chicken mousse, together with the ham and sage. (You can use the rest of the mousse to stuff mushrooms: cover them with breadcrumbs and bake with garlic butter for a wonderful first course.)
Spoon the mousse mixture on top of the trotters, line them up and roll them up together to make a sausage. Roll up the cling-film around them, then roll the package in foil.
Steam the packages for 20 minutes.
While the trotters are steaming, make the Potato Baskets: preheat the oven to 190°C/375°/gas 5. Peel the potato and cut it into very fine matchstick strips or grate it finely. Season with salt and pepper and leave for a few minutes to allow the salt to draw out the moisture from the potato. Squeeze it out in a clean tea towel. Add the clarified butter and mix in well.
Press the mixture into 4 individual brioche moulds to line them and then press another similar mould inside each to hold it in place. Bake in the oven until the potato is golden, about 7-10 minutes. Allow to cool and then turn the baskets out of the mould.
At the same time, make the Shallot Sauce: put the shallots in a pan, pour in the port and add 100ml / 3½fl oz. water. Add the sugar and cook until almost all the liquid has evaporated.
At the same time in another pan, boil the mixed stocks down until they have a good sauce-like consistency. Mix into the pan of shallots and adjust the seasoning if necessary. Reserve.
Make the Pea Purée: cook the peas in a pan of boiling salted water until just tender, about 1 minute. Refresh in iced water and drain in a colander. Purée in a blender or food processor and pass through a fine sieve. Reheat to serve.
Allow the trotters to cool slightly, then cut them into slices. Put a potato basket in the middle of each plate, then place a spoonful of pea purée in each basket. Arrange 3slices of trotter around each basket and 3spoonfuls of the shallot sauce in between the medallions of trotter.