Make the dressing by combining the lemon, mustard, garlic, salt and pepper,

Add the oil in a stream, wisking until emulsified. Taste and correct as needed.

In a stainless steel or enameled kettle combine the mussels, the clams, the wine and the cheesecloth bag and bring to a boil, steaming the shellfish, covered and shaking the kettle once or twice, for about 5 to 7 minutes or until the shells have opened. Discard any unopened shells.

Transfer with a slotted spoon to a large bowl, reserving the cooking liquid, and shell them, removing the black rims from the mussels if desired.

Toss the shellfish with the dressing until well coated.

Strain the reserved cooking liquid through a fine seive lined with cheesecloth into a measuring cup, add enough water to make 2 cups.

Bring this liquid to a simmer in a stainless saucepan and poach the scallops and squid for 1 to 2 minutes or until the scallops are just opaque. Transfer the seafood with a slotted spoon to the bowl with the shellfish and toss the mixture well.

Bring the liquid to a simmer and poach the shrimp for 2 to 3 minutes.

Transfer with a slotted spoon to the bowl and toss well and chill covered for at least 2 hours or overnight.

Add the celery or fennell, olives, capers, salt and pepper to taste toss and let come to room temperature.

Meanwhile broil the peppers on the rack of a broiler pan under a preheated broiler about 4 inches from the heat, turning frequently, for 12 to 15 minutes or until they are blistered and charred, enclose them in a paper bag, and let them steam until they are cool enough to handle. Peel , halve them lengthwise, and discard the ribs and seeds. ( The peppers may be stored covered and chilled, for up to 2 days.)

Arrange the peppers on the plate and mound the seafood salad on the plate.