Put the hare pieces in a 3-liter / 3-quart non-reactive lidded container with the onion, carrot, celery, garlic, juniper, bay, rosemary, cloves and peppercorns. Pour over the wine so the meat is mostly submerged, then cover and refrigerate for 12 hours, turning the pieces once halfway.

Heat the oven to 150 C / 300 F. Lift the hare out of the marinade and pat each piece very dry with paper towels. Strain the marinade over a bowl, keeping the liquid and the solids, and pick the bay and rosemary out of the solids for later.

Toss the dry hare with the flour and 1 tsp salt, shaking off the excess. Heat the olive oil and butter in a 28 cm / 11-inch (5-quart / 4.7 L) Dutch oven over medium-high heat. Brown the hind legs and forelegs first, 3 to 4 minutes per side, until deeply golden, then transfer to a plate. Brown the saddle pieces and ribs as a second batch and set them aside separately.

Lower the heat to medium and add the pancetta. Cook for 4 minutes until the fat renders, then add the drained vegetables and cook for 6 minutes until softened and browned at the edges. Stir in the tomato paste for 1 minute.

Pour in the strained marinade liquid, scraping up the browned bits from the base. Simmer for 4 minutes to cook off some of the alcohol, then add the stock, bay and rosemary. Return the legs and forelegs to the pot, bring to a bare simmer, cover and bake for 60 minutes.

Add the saddle pieces and ribs, pushing them under the liquid. Cover and bake for another 60 minutes, until a fork slides into the thickest part of a leg with no resistance.

Lift the hare onto a plate and cover with foil. Skim the fat from the surface, discard the bay and rosemary, and simmer the sauce on the stovetop over medium heat for 8 minutes until it coats the back of a spoon. Stir in the chocolate, then taste and add the remaining salt.

Return the hare to the pot, spoon the sauce over and warm through for 2 minutes. Serve hot over polenta.