Heat two tablespoons of oil in a frying pan and fry the Rösti in it over a low heat for eight minutes on each side, turning occasionally until golden brown. In the meantime, peel and finely dice the onion.
Clean, wash and cut the leek into thicker slices. Wash and quarter apples and cut out the core. Cut apples into slices and sprinkle with lemon juice. Heat the remaining oil in a pot.
Sauté the onion briefly in it. Add leek and apples and stew for three to four minutes. Season with salt and pepper. Add stock and cream, bring to the boil and cook over a low heat for another five minutes.
Bind with sauce thickener. In the meantime, put 375 millilitres of water and 1/2 teaspoon of salt in a pot and bring to the boil. Remove from heat and add milk. Stir in puree flakes. Stir again after one minute.
Season vegetables again and arrange on plates together with mashed potatoes and ham rösti. Serve garnished with dill and dill blossoms as desired.