Oysters Rockefeller

Preheat oven to 450°F (230°C).

Fill 4 tin pie plates with rock salt and arrange 6 oysters on the half shell on each.

In a skillet over medium heat, melt the butter. Add the parsley, celery, shallots, and garlic and cook 3 minutes. Add the watercress and fennel and cook until the watercress wilts, about 1 minute. Transfer the mixture to a food processor, add the remaining ingredients, and blend until the sauce is thoroughly puréed.

Place 1 tablespoon sauce on each oyster and spread to the rim of the shell. Bake the oysters just until the sauce bubbles, about 4 minutes. Serve immediately.