Clean and rinse the fish, then place it in a pan, cover with salted water and stew it with sage leaves. Once drained, bone it and break the meat. Finely chop the onion, lightly fry in until soft, then, once rinsed and chopped into strips, add the lettuce.Season with salt and a generous grind of pepper and nutmeg. Cover it with water and, once covered with a lid, simmer for 10 minutes over a low heat. Remove the heat and let the cooking water evaporate.Once the lettuce is reduced, add the chunks of fish and sprinkle with brandy. Flavour for a few minutes then switch off the heat. Once whisked with the milk add the egg, stir well with a wooden spoon and sprinkle with chopped parsley.Cook the pasta in a pan with plenty of boiling salted water, drain it when al dente and serve it in individual deep dishes with 1/4 of the sauce.