Cut the Speck into small pieces.
Heat a small spoonful of oil in a large saucepan and add the Speck. Fry until it realises its fat and starts becoming crispy.
Add the garlic and rosemary, stir for a few seconds, then add the paprika and cornflour. Stir to coat the speck bits, then add the tomato purée and pour in a ladleful of stock. Cook for a couple of minutes until smooth, then add the rest of the stock. Add the beans and bay leaves, then bring to the boil.
Cook for 60-75 minutes over low heat, under cover until the beans are just tender.
Peel the celeriac and carrots, cut them into chunks. Add these to the soup and cook for a further 30 minutes or so, until the beans are and veggies are tender.
Cut the sausage into chunks and add to the soup, together with the parsley. Cook for 5 minutes.
Turn off the heat and stir in the vinegar. Remove the parsley.
Serve with sour cream, if liked.