Cook the spaghetti according to the instructions on the packet and then drain.
Cut the spring onions diagonally into rings and fry in 2 tablespoons of oil over a medium heat. When the onions are still bite, add the cream, the juice of half a lemon, salt, pepper, sugar and nutmeg and bring to the boil.
Remove from heat and stir in creme fraîche or sour cream and sour cream. Then add the spaghetti, mix everything and sprinkle some freshly grated parmesan on top.