Peel, wash and halve the potatoes. Cut pumpkin into quarters, remove seeds. Peel the flesh and cut into pieces. Cook potatoes and pumpkin pieces in boiling salted water for 20-25 minutes.
Meanwhile roast pumpkin seeds in a pan without fat. Take out and let cool lukewarm, chop coarsely. Wash the fish, dab dry and season with salt and pepper. Turn fillets in flour, knock off excess flour.
Heat the oil in a large frying pan. Fry the fish fillets for 6-8 minutes while turning. In the meantime heat milk and butter in a small pan. Drain pumpkin and potatoes, add milk and mash coarsely.
Season to taste with salt and nutmeg. Arrange the puree on plates. Place fish on top. Sprinkle with pumpkin seeds. Drizzle pumpkin seed oil around the puree. Possibly garnish with parsley leaves.