Rinse mussels thoroughly and discard any that don’t close when handled. Place in a large pot; add water, vinegar and onion, and bring to a boil. Mussels are done when they have opened, about 5 to 6 minutes.

Remove from pot with a slotted spoon; strain the cooking broth into a medium saucepan and keep warm over low heat.

Drain mussels well and let cool slightly in a deep serving dish before removing meat from shells; cover and keep warm. Reserve a few shells to dress the serving plate and place a serving plate in a low oven to warm.

In a small bowl, mix egg yolks and lemon juice. In another medium saucepan, warm the butter over medium heat; add mussel meat and lightly brown. Cover and keep warm.

Remove cooking broth from heat and add the egg yolk mixture; beat lightly. Return to heat for 2 minutes, but do not boil or the yolks will separate. Add salt and pepper to taste.

Place mussels on the warm serving plate. Pour 
sauce over top; sprinkle with chopped herbs and 
garnish with a few shells. Serve immediately. 
Makes 4 servings.