Remove any sinew from the venison, then place the meat in a large bowl. Add the peppercorns, juniper berries, if using, thyme, and one onion, thickly sliced, plus the wine and olive oil and mix together thoroughly. Cover and chill for 24 to 48 hours.

Drain the venison, reserving the marinade, but discarding the onion. Pat the meat dry with kitchen paper. Heat 2 tablespoons of the sunflower oil in a flameproof casserole and brown the venison all over, in batches, over a high heat.

Preheat the oven to 170°C/150°C fan oven/Gas Mark 3. Add the pancetta to the casserole and fry for 5 to 10 minutes until browned, then remove the venison and pancetta and set aside. Add the remaining sunflower oil, lower the heat to a moderate setting, and fry the remaining onion, finely chopped, and the garlic for 10 minutes or until golden. Stir in the flour, then the reserved marinade. Bring to the boil and bubble for 2 to 3 minutes.

Return the venison, any juices and the pancetta to the casserole, with the stock and the bay leaf. Season to taste. Bring to the boil, cover and simmer for 5 minutes, then transfer to the oven and cook for 1 hour 15 minutes or until tender (venison marinated for 48 hours probably needs slightly less time). Meanwhile, place the shallots in a pan of cold water, bring to the boil and simmer for 3 to 4 minutes, then drain, leave to cool a little, then peel.

Heat the butter in a medium-sized frying pan, add the shallots and the sugar, then cover and cook for 15 to 20 minutes until the shallots are soft to the centre and a sticky golden brown. Add the chestnuts and cranberries, stir the mixture well and cook for a further 2 to 3 minutes.

Remove the venison from the oven 5 minutes before the end of cooking time. Stir the shallot mixture into the stew and return to the oven for a further 5 minutes.