Mussels on the Half Shell with Ravigote Sauce

Name: Mussels on the Half Shell with Ravigote Sauce
Ingredients: 48 mussels (preferably cultivated; about 1 1/2 lb), scrubbed and beards removed; 1/4 cup dry white wine; 1 hard-boiled large egg; 1/2 cup olive oil; 3 tablespoons white-wine vinegar; 1 medium onion, finely chopped (1/2 cup); 2 teaspoons drained bottled capers, rinsed, chopped if large; 1 teaspoon Dijon mustard; 1 teaspoon finely chopped fresh flat-leaf parsley; 1 teaspoon finely chopped fresh chervil; 1 teaspoon finely chopped fresh chives; 1/4 teaspoon salt; 1/8 teaspoon black pepper