Combine first 4 ingredients in an extra-large kettle or soup pot; bring to a boil over high heat. Add crabs; cover and boil 12 to 15 minutes or until crabs turn bright red. Rinse crabs quickly with cold water; drain well, and cool. Remove top shell from crabs; reserve for garnish, if desired. Clean crabs, removing gray gills and mouth parts; break in half. Cover and chill. Serve with lemon wedges, Sea Salt Butter, and Ginger Mayonnaise.
Note: If you aren't sure the crabs are done, pull off a top shell and look at the meat; it should be white and opaque, not translucent.