Clean the leek and cut it lengthways. Then wash thoroughly and cut into fine strips. Heat the oil and fry the leek for about 5 minutes over low heat. Press the bratwurst out of the skin in small pieces and add to the leek, stir-fry for 3 minutes.
Mix the crème fraiche and the cream together. Add and cook for 5 minutes. Season to taste with salt, pepper and nutmeg.
Cook the pasta until al dente according to the instructions on the packet. Drain, drain briefly and mix with the sauce.