Pour the milk into a saucepan, add the herbs, cloves and onion and bring to the boil. Remove from the heat, cover and leave to infuse for 1 hour.
Meanwhile, steam the potatoes until soft and pass them through a sieve into a bowl. Add the chopped turkey, ham, mushrooms, chives and nutmeg. Season well and combine.
Strain the infused milk through a sieve into a jug, discarding the herbs, cloves and onion. Melt the butter in a saucepan, stir in half the flour and cook on medium heat for 1 minute. Gradually stir in the infused milk, then bring the mixture to the boil, stirring continuously until the sauce thickens and leaves the side of the pan. Stir the sauce into the turkey mixture, cover and chill for 1 hour.
Put the remaining flour on a plate and season lightly with salt and ground black pepper. Using a fork, whisk the egg and milk together lightly on a second plate and put the breadcrumbs on a third plate. With slightly dampened hands, take about 3 tablespoons of turkey mixture and roll into an oval. Make another 17 croquettes in the same way. Coat each in the seasoned flour, then dip into the egg and roll in the breadcrumbs. Reshape the croquettes by rolling them in your hands. Put onto a baking tray, cover and chill for 30 minutes, or until required.
Heat the oil in a deep frying pan until a cube of stale bread dropped into the oil browns and rises within 20–30 seconds. Fry the croquettes, in four batches, for 8–10 minutes, turning them frequently until they are evenly golden. Drain on kitchen paper and keep hot.
Serve with jacket potatoes, cranberry relish and a tossed green salad, if desired.