After the rouille is made, clean the mussels by placing them in a pot of fresh water. Examine each mussel, discarding any with broken shells.
Scrub each mussel and remove the"beard". Reserve cleaned mussels in a bowl.
In a large stockpot, combine the wine, garlic, ground pepper, and enough water to bring the stock up to a depth of three inches.
Bring the pot to a boil, cover, and then simmer for 15 minutes over low heat.
Remove the lid from the pot and carefully place the mussels in the pot.
Cover the pot and simmer over medium-high heat until the mussels just open (about five minutes). Don't overcook the mussels.
Lift out mussels, place in a bowl, and cover to keep warm.
To serve, place mussels in individual soup bowls. Ladle some of the stock over the mussels and then add a dollop of rouille. Serve with slices of crusty bread to dip in the fragrant stock and more rouille as desired.