Mussels must be thoroughly cleaned with a knife or a metal washcloth, and rinsed in water several times. Put them into a deep frying pan with water, parsley and black pepper. Put on the fire and simmer for 3 minutes after the water boils until all the mussels open. Then remove them from the fire, partly remove the shells, and leave some shells for a beautiful decoration of the dish.
Boil spaghetti in the salted water until cooked.
Put spaghetti, peeled mussels, chopped tomatoes, garlic and parsley into the frying pan. Add spaghetti broth (1/2 cup). Stir well and simmer for 5 minutes.
Put in a deep dish, decorate with mussels in the shells.