1. Coat the duck pieces with the rock salt and set aside for 30 minutes.
2.Preheat the oven to 220C (200C fan-forced).
3. Wipe the salt from the duck pieces with a damp paper towel. Arrange on a rack over a roasting tray and roast skin side up for 30 minutes until golden and a lot of fat has rendered into the tray.
4.Add the 60ml of olive oil and butter to a wide-based saucepan over medium heat. Add the onion,leek and garlic,season and sauté for five minutes until softened. Add the celeriac and carrot and cook for 15 minutes until caramelised. Stir through the thyme,bay leaves and allspice. Add the duck,verjuice and wine and simmer for five minutes.
5. Add the stock and simmer very gently for a further 40 minutes until just before the meat falls off the bone. Remove the duck and cut the meat and skin into largish chunks. Reduce the liquid to a sauce consistency,then return the meat to the pan. Adjust seasoning to taste.
6. Cook the pasta in plenty of boiling salted water,then drain briefly and toss through the ragout with a handful of parmigiano.
7.Combine the saba and peppery oil in a medium bowl with salt and pepper to taste. Toss the radicchio through the dressing and serve the pasta with the dressed radicchio on top and extra parmigiano on the side.
Note: Finishing with radicchio may seem somewhat odd,but the dressed,jewel-coloured leaves add a welcome sweet-and-sour bitterness to the rich sauce.