Peel, wash and quarter the potatoes. Cook in a large pot in boiling salted water for about 20 minutes. Wash the pumpkin, remove seeds, dice the flesh roughly and add to the potatoes after about 10 minutes.
Peel onion and cut into rings. Wash the apple, cut out the core and cut the fruit into slices. Heat 1 tablespoon of oil in a frying pan. Fry the onion rings for about 4 minutes. Season with salt. Take out and turn the apple rings in the onion fat. Deglaze with 6 tbsp. water, fry apple slices and onion rings for about 4 minutes.
Wash parsley, shake dry, pluck leaves from the stalks and chop. Bring milk and 4 tablespoons of oil to the boil. Drain potato-pumpkin pot. Add milk and oil and mash with a potato masher until puree. Season to taste with salt, nutmeg and lemon juice. Arrange puree, apple slices and onion rings. Sprinkle with parsley