After cleaning the mussels well, put them into a very large heavy pot with all the other non-sauce ingredients plus 1/4 cup of water. Put the pot over high heat and bring the liquid to a boil. After a couple of minutes, vigorously shake the pot to allow the unopened mussels to work their way to the bottom and open. Steam for about four minutes, or until all the mussels have opened.
Remove the mussels to a strainer over a bowl to catch all the juices. After they cool for three or four minutes, rinse the inside of the shells in a bowl of water, and remove any beards that may remain.
Add the collected mussel juices back to the pot and strain through the finest strainer you have or cheesecloth.
To begin the sauce, heat the butter in a large saucepan until it bubbles, and make a blond roux with the flour. Add the onion, garlic, and crushed red pepper. Cook for about two minutes--until the garlic is fragrant.
Add the mussel juices and, over medium-low heat, bring to a light boil and hold there for about eight minutes. Add the cream, saffron, and parsley, and return to a light boil for about three or four more minutes. Add salt and black pepper to taste.
Place a dozen mussels in a large broad-rimmed soup bowl, and ladle the sauce over them. Top with chopped green onions. Provide hot loaves of French bread, damp towels, and a bowl for the shells.
