Soak rolls in cold water. Quarter the pumpkin and remove the seeds and fibres. Peel pumpkin and dice roughly. Peel, wash and cut potatoes into large pieces. Cover the potatoes and pumpkin and cook in boiling salted water for about 25 minutes.
In the meantime, squeeze out rolls for the meatballs. Peel onions. Chop 1 onion finely. Knead minced meat, bread roll, egg, diced onion, mustard and approx. 1 tsp salt and pepper each. Form approx. 8 meatballs from the minced dough with moistened hands.
Heat 1 tablespoon of oil in a large frying pan. Fry the meatballs in it over medium heat for 6-8 minutes on each side.
In the meantime, wash the parsley, shake dry and chop the leaves finely. Cut the rest of the onions into rings. Wash apples and core them with the apple corer. Cut apples into thin rings.
Remove the meatballs from the pan and keep warm in a hot oven (approx. 50°C). Heat the butter in the frying fat. Fry the onion rings until golden brown, turning them over. Add apples and fry briefly.
Drain the pumpkin vegetables, add 3 tablespoons of oil and mash everything with a potato masher. Season to taste with salt, nutmeg and lemon juice. Serve the puree and meatballs with apple and onion rings.
Sprinkle with parsley.