Combine first 7 ingredients in a large skillet.
Bring to a boil over medium-high heat, stirring occasionally.
Remove from heat, and transfer mixture to a large bowl; cover and chill thoroughly.
Wash artichokes by plunging up and down in cold water.
Cut off the stem end, and trim about 1/2 inch from top of each artichoke.
Remove any loose bottom leaves.
With scissors, trim away about a fourth of each outer leaf.
Rub top of artichoke and edges of leaves with a lemon wedge to prevent discoloration.
Place artichokes in 2 inches of water in a large Dutch oven.
Cover and bring to a boil; reduce heat, and simmer 30 to 35 minutes or just until outer leaves pull off easily.
Place artichokes upside down on a rack to drain; chill thoroughly.
Spread outer leaves of each artichoke apart; scrape out the fuzzy thistle center (choke) with a spoon.
Drain shrimp and scallops; spoon mixture into center of each artichoke.
Serve with Mustard-Vinaigrette Sauce for dipping.