In a medium saucepan, melt the butter over medium
heat. Add the leeks, shallots, celery, and mushrooms. Sauté until tender
but not colored. Add the wine and oyster liquor and reduce by half. Add
the heavy cream and reduce until nappé, slightly thickened. Add the lemon
juice, oysters, and tomatoes. Spoon the stew into center of soup plate.
Arrange toasts around and garnish with chives and tarragon.