Briefly roast the chopped onion in a pan with a little oil. Add the sliced chicken breast fillet and fry well all over. Then add the sliced pumpkin and bell pepper and mix everything well. Pour in the vegetable stock and bring to the boil. Season with salt, pepper and ground nutmeg and cover and simmer gently for about 5-10 minutes (depending on the size of the pumpkin pieces). The pumpkin should be soft but still bite.
Then stir in the creme fraiche and let it boil down briefly. Maybe a little more seasoning.