This oyster stew can be transformed from a comforting one-pot meal to an elegant dish for guests when you top it with caviar toasts: dollop toasted slices of baguette with 1 teaspoon sour cream, 1/2 teaspoon caviar and a sprinkle of herbs. Place each toast atop a steaming bowl of stew. Serve with a salad of butter lettuce, orange segments and red onion tossed with vinaigrette.