Combine the venison chunks, 500 ml of the red wine, carrot, celery, onion, garlic, juniper berries, bay leaves, rosemary, cloves, and peppercorns in a large bowl. Cover and refrigerate for at least 12 hours, up to 24.

Lift the venison out of the marinade and pat it fully dry with paper towels. Reserve the marinade with its vegetables and spices.

Heat the olive oil in a 26 cm / 10-inch Dutch oven over medium-high heat. Sear the venison in two batches, 3 to 4 minutes per side, until deeply browned. Transfer to a plate.

Reduce the heat to medium and add the pancetta and butter to the same pot. Cook, stirring, until the pancetta is golden, about 3 to 4 minutes.

Add the reserved marinade vegetables, spices left in, and cook until softened, 6 to 8 minutes.

Stir in the tomato paste and cook for 1 minute, until it darkens slightly.

Return the venison to the pot along with the reserved marinade liquid, the remaining 250 ml red wine, and the stock. Bring to a gentle simmer.

Cover the pot and transfer it to an oven preheated to 150 C / 300 F. Braise for 2 to 2.5 hours, until the venison is fork-tender and pulls apart easily.

Remove the pot from the oven and fish out the bay leaves and whole cloves. Stir in the grated dark chocolate until it melts into the sauce.

Season with salt and pepper. If the sauce looks thin, simmer it uncovered on the stovetop for 5 to 10 minutes to thicken.

Spoon the capriolo in salmi over soft polenta and serve hot.