Peel and shell the prawns, scallops, sea walnuts and clams. Cut them all into small cubes and brown quickly in a non-stick pan with a hint of white wine, before adding a little salt and a touch of diced parsley. Cook the spaghetti in salted water for 8 minutes, drain and add to the fish sauce along with one egg yolk. Remove from the heat and mix carefully, then grating the roe shavings and Piave cheese over the top. Serve immediately.