Combine meat, wine, carrots, celery, olive oil, thyme, parsley, pepper and juniper. Cover and marinate overnight. Remove meat from the marinade. Save marinade and saute meat and bacon in a bit of olive oil until well browned. Sprinkle with flour and saute for 3 minutes. Remove vegetables from marinade, saving marinade. Add to the meat and saute for 5 minutes. Add marinade, bring to boil, add stock. Bring to a boil again, reduce heat and simmer for 2 hours. Add chocolate to the sauce, stir until melted. Add butter, stir until melted. Season with salt and pepper and serve with boiled potatoes.