Wash and dry meat well. Put in a porcelain or glass bowl. Peel and slice the onions and the carrots and place on top of the meat. Add the bayleaf and the peppercorns and then pour the wine and the buttermilk over it all. Let the meat marinade for 3 days, turn it over daily. Cut the bacon in cubes and fry it in the butter until it is crisp. Add the meat and lightly brown on all sides. Add 2 tablespoons of  the marinade and simmer for 10 minutes more. Add the tomato paste and the crumbled rye bread and salt to taste. Add the carrot and onion slices and simmer on low for about 1 1/2 hrs. Turn the meat often and replace water, if necessary. Strain the gravy and thicken with a little cornstarch if desired. Traditionally served with wide noodles, or mashed potatoes and carrots or mixed vegetables. Try out more marinade to adjust to your taste. Serves 6