Heat the oil in a pan. Sweat the onions and garlic with turmeric and black pepper. Add the pumpkin meat and fry for 5 minutes. Deglaze with white wine and cover and simmer for 5 minutes over low heat.
Bring the water to the boil, dissolve the stock powder in it and add to the pan with the chestnuts, cover and simmer for another 10 minutes.
In the meantime, grate the cheese and add to the sauce in the pan with the finely chopped chilli pepper, ginger and marjoram. Stir until the cheese has melted.
Mix the cream and sour cream in a glass with a fork or whisk until smooth. Turn off the stove and stir the cream and sour cream mixture into the sauce. Possibly season with a little cayenne pepper.