In a large, nonreactive pot bring 6 quarts of water to a boil and add artichokes. Squeeze juice from the lemon halves into water, then add peels along with the bay leaves and salt. Cover, reduce heat to simmering and cook until artichokes are tender, and base can be pierced with tip of a knife, about 25 minutes. Drain artichokes. When artichokes are cool enough to handle, trim the stems from base, to make the bottoms flat. Cut off 1-inch of leaves from top. Placing the artichokes on their base, spread apart the outer leaves and carefully remove and discard the center section and fuzzy choke, leaving outer leaves intact.
In a bowl combine the seafood, lettuce, radicchio and vinaigrette. Season to taste with salt and pepper and toss well. Using a slotted spoon, fill each artichoke cup with about 1 cup of seafood salad. To serve, drizzle some of remaining vinaigrette over artichokes.
Yield: 6 Servings