Marinated Mussel Salad

Place mussels, onion, water and wine in a large saucepan. Cover and bring to a boil over high heat. Cook just until the mussels open, 2 to 3 minutes. Drain, cool and shell the mussels, discarding any that do not open.

Combine lemon juice, parsley, oil, capers, mustard and pepper in a medium bowl. Add the shelled mussels; marinate for at least 5 minutes.

To serve, divide lettuce between 2 plates and top with the mussel mixture.