Put the leg of venison in a large container with the sliced vegetables, peppercorns and bay leaves, pour over the red wine and vinegar, cover and marinate in the fridge for at least 24 hours (up to 2-3 days), turning daily.
Remove the marinated leg, pat lightly dry, and lard it with bacon strips using a larding needle.
Place in a roasting pan, spread with the lard, and pour over the marinade vegetables together with the marinade.
Season with salt, and place in a preheated 180°C oven.
Roast for about 1.5-2 hours, basting frequently with its own juices, until nicely browned and the meat is tender.
Once browned and tender, remove from the pan and rest, covered, for a few minutes.
Stir a tablespoon of flour into the remaining fat and juices, bring to a boil, then push through a sieve together with the vegetables in it.
Stir in the sour cream, bring to a boil, and season with salt to taste.
Slice the meat and serve drizzled with the sauce.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.