Slice both the escalope pieces through the centre crosswise to within 1 cm (1/2 in) of the end of the meat. Pull apart and lay flat on a working surface. Cover the meat with a layer of greaseproof or waxed paper and pound for 2 to 3 minutes or until the meat is slightly thinner. Remove the paper and trim the edges to neaten them. On the larger piece place the prosciutto, pork fat and carrots, and season with salt and pepper. Lay the smaller piece on top, then spread over the liver sausage. Arrange the truffle and pepper lengthways down the centre and roll up Swiss (jelly) roll style, tying firmly with string at about 2 1/2 cm (1 in) intervals.

Preheat the oven to moderate 180°C (Gas Mark 4, 350°F).

Melt the butter in a large flameproof casserole. Add the shallots and fry until they are soft. Add the meat and fry until it is evenly browned. Pour over the Marsala and stock and bring to the boil. Cover and transfer the casserole to the oven. Cook for 1 to 1 1/4 hours, or until the veal is cooked through and tender. Remove from the oven and transfer the meat to a warmed serving dish. Untruss and keep hot while you finish the sauce.

Bring the cooking liquid to the boil, then boil briskly for 5 minutes, or until it has reduced slightly. Reduce the heat to low and stir in the beurre manie, a little at a time, until the sauce thickens and becomes smooth.

Pour into a warmed sauceboat and serve at once, with the meat.