Rinse the meat, pat dry and cut into 2 cm (approximately 3/4-inch) cubes. Peel the onions and garlic, chop the garlic finely and cut the onion into strips. Heat the oil in a Dutch oven and working in batches, brown the meat all over and remove with a slotted spoon. Once all the meat has been browned, return it to the pan and add the onions and garlic and saute until the onions are translucent. Stir in the tomato paste and sauté briefly. Add enough broth to barely cover the meat. Add the paprika, juniper berries and bay leaf and season with salt and pepper. Bring to a boil, reduce to a simmer, partially cover and cook over low heat adding more broth if necessary, for 1 hour.
Add the sauerkraut and simmer 30 minutes.
Season with salt, pepper and cayenne pepper, stir in the sour cream and serve.