Place in a large soup pot:
Cover and steam over medium heat until the mussels open; discard any that do not open. Remove the mussels and set aside. Strain the cooking liquid through a sieve lined with several layers of dampened cheesecloth or paper towels into a medium saucepan. Bring to a simmer. Remove the mussels from their shells. Whisk together in a small bowl:
Gradually whisk about 1 cup of the cooking liquid into the egg mixture, then whisk back into the saucepan. Heat through, but do not boil. Season with:
Garnish with the reserved mussels and sprinkle with: