Usually the mussels will be de-bearded when purchased, however, if the mussels still have their "beards" (byssal threads), wait until within an hour of cooking to remove the mussel beards by giving them a sharp pull toward the pointed tips of the mussels. Lightly rinse the mussels under fresh, running water before cooking, then set aside. If any mussels are gaping open, they are getting weak, discard any that will not attempt to stay closed after squeezing their shell shut or if they have broken shells or an "off' odor.
To make the sauce, heat the olive oil in a large saucepan, add the onions, celery, garlic, basil and bouquet garni, and cook over low heat for 5 minutes or until softened but not browned.
Mix in the tomato paste and tomatoes, salt, pepper, and sugar, and simmer gently for 30 minutes.
Put the mussels in a casserole dish with the wine, over high heat, and bring to a boil. Cook for a few minutes only, until the mussels have opened, stirring frequently to ensure they are evenly cooked.
Pour off the cooking liquid, discard any mussels that have not opened, and return the opened mussels, in their shells, to the casserole dish.
Pour the hot tomato sauce over the mussels and heat through. Sprinkle with chopped basil and serve at once.
From: The Belgo Cookbook by Denis Blais and André Plisnier