In a saucepan, sauté the carrot, onion and celery slices in half the oil until soft but not browned.
Add the wine, wine vinegar, bouquet garni, juniper berries and peppercorns and bring to a boil. Simmer until the vegetables are tender, 15-20 minutes. Add the remaining oil and leave to cool.
Put the meat in a deep bowl and pour over the marinade so th