Chilled Mussels on the Half Shell with Mignonette Sauce

Scrub mussels; remove any beards. Discard any mussels that do not close when tapped.

In large pot or Dutch oven, bring white wine to boil over medium-high heat. Add mussels; cover tightly and cook over high heat until mussels open, about 8 minutes. Discard any that do not open.

Remove mussels from liquid and remove from shell, reserving half of each shell; cover and refrigerate mussels.

Strain cooking liquid through cheesecloth-lined sieve into clean saucepan. Add chopped shallot and bring to boil over medium heat; reduce heat and simmer until reduced to oe cup (50 mL), about 10 minutes. Transfer to bowl; let cool.

Stir parsley, vinegar and capers into reduced cooled liquid. Add mussels and toss to coat. Cover and refrigerate for 4 hours. (Make-ahead: Refrigerate for up to 24 hours.)

Arrange mussels on shells. Drizzle any remaining cooking liquid over top.