Mussels in parsley vinaigrette

1 / 2 cup plus 3 tablespoons extra-virgin olive oil

1 / 2 cup thinly sliced shallots, plus

1 tablespoon finely chopped (about 3 total)

1 / 2 cup dry white wine

3 pounds mussels (about 100 small), scrubbed and debearded

1 teaspoon Dijon mustard

3 tablespoons rice-wine vinegar

Coarse salt and freshly ground pepper

3 tablespoons finely chopped fresh flat-leaf parsley, plus leaves for garnish

Lettuce leaves, for serving (optional)

Heat 2 tablespoons oil in a large pot over medium heat. Add the sliced shallots; cook, stirring, until translucent, about 3 minutes. Add the wine; bring to a boil. Add the mussels; cover and cook, stirring once, until the mussels open, about 3 minutes. Discard unopened shells.
Remove the mussels with a slotted spoon; discard the cooking liquid. Chill the mussels in a bowl in the refrigerator, about 1 hour.
Whisk together the mustard, chopped shallots, and vinegar; season with salt and pepper. Pour in the remaining 1 / 2 cup plus 1 tablespoon oil in a slow, steady stream, whisking until emulsified. Whisk in the parsley. The vinaigrette can be stored in the refrigerator up to 3 days.
Toss the chilled mussels with 1 / 2 cup vinaigrette. If desired, serve on the half-shell on a bed of lettuce. Garnish with parsley. Drizzle with more vinaigrette, if desired.

SERVES 4 TO 8