Remove the peel and seeds from the pumpkin and cut into bite-sized cubes. Peel the potatoes and also dice them. Remove the leaves from the celery, chop the leaves and set aside (for garnish).
Cut the onions and celery into fine pieces and fry them in melted butter in a large saucepan. Gradually add the pumpkin and potatoes, season with salt and pepper and stir everything well. Pour the broth over the top and simmer for about 25 minutes, stirring frequently.
Then drain the vegetables and liquid and set them aside separately.
Mix the flour, water and sour cream well and mix with the liquid. Bring the sauce to the boil briefly. Stir in the vegetables and season to taste with nutmeg, parsley, salt, pepper and the curry paste. Then sprinkle with the chopped celery leaves and serve in deep plates.