To put the spaghetti in 3 liters water in ebullition with addition of ½ teaspoon of salt. To cook the spaghetti at least 8-9 minutes. Before pasta is cooked, to middle fire we will start heating the egg in an enough capacious frying pan. In the frying pan we will also put the garlic and we will let brown the all, mixing for around 30 seconds. To this point we can add the watercress, the salmon and the pepper. The cooking will continue for others 30-40 seconds. Drain in a frying pan the pasta, to mix for amalgamating it with the sauce. To serve warm.