Peel and wash the potatoes and kohlrabi and cut into small pieces. Clean and wash the leek and cut into fine rings. Heat the lard. Steam leek in it. Add bay leaf and peppercorns. Fill up with broth, bring to the boil briefly.
Cover the prepared vegetables and cook for about 30 minutes. Then mash until slightly mushy. Season to taste with salt and pepper. Cut ham into small cubes and add to the stew. Serve in portions garnished with tender kohlrabi leaves