8 tablespoons unsalted butter, plus 3 tablespoons, melted, for brushing
1 medium onion (5 to 6 ounces), finely diced
2 sprigs tarragon, leaves picked and coarsely chopped (2 teaspoons)
2 sprigs Italian parsley, leaves picked and coarsely chopped (2 tablespoons)
4 ounces peeled raw Maine shrimp or raw scallops or cooked crabmeat or lobster meat, cut into 1/2-inch dice
Kosher or sea salt
Freshly ground black pepper
2 live 1 1/2 to 2 1/2-pound hard shell select lobsters
3 ounces common crackers, oyster crackers, or dried corn bread, crumble