Wash the beef and place in a bowl. Mix the wine and vinegar, then pour over the meat until completely covered.
Peel and halve the onion and carrots. Add them to the meat along with the peppercorns, bay leaf, and salt. Cover the bowl and refrigerate. Marinate for at least 3 days, turning the meat once each day.
Remove the meat from the marinade and pat it dry thoroughly.
Heat oil in a large pan over medium-high heat. Fry the meat vigorously on all sides until well browned. Add the onion and carrots from the marinade and the flour. Pour in roughly 500 ml (2 cups) of the remaining marinade and bring to a simmer. Cover and simmer for approximately 1.5 hours, adding more marinade as needed to keep the meat mostly covered.
Remove the meat from the pot and set aside to keep warm. Discard the onion and carrots. Stir the sour cream into the cooking liquid and bring to a boil over medium-high heat, stirring for 1-2 minutes. Season with salt and pepper to taste. Let the roast rest for 10 minutes before slicing.