This renowned baked oyster dish was created at Antoine's Restaurant in New Orleans in 1899 by the proprietor, Jules Alciatore. According to legend, the dish was created as a substitute for baked snails, which were hard to obtain from France. It was named in honor of John D. Rockefeller, at that time one of the world's richest men, because of the sauce's intense richness. The following recipe is the old Delmonico restaurant's take on the dish, with the Rockefeller sauce base used not only to make the Oysters Rockefeller appetizer, but also used as a spread on toast to create canapés.
Preheat the oven to 400°. Spread a 1/2-inch-thick layer of rock salt on a large baking sheet and across the bottoms of 6 large plates.
Arrange the reserved oyster shells on the baking sheet. Put 1 oyster in each shell and top with 2 to 3 tablespoons of the sauce, spreading the sauce evenly out to the edge of the shell to completely cover the oyster. (Alternatively, transfer the sauce to a pastry bag fitted with a plain tip and pipe the sauce over the oysters.)
Bake until the sauce is lightly browned and the oysters begin to curl around the edges, about 20 minutes.
Using tongs or a spatula, carefully transfer the hot shells to the salt-covered plates and serve immediately.