24oysterslarge, with deep half-shells (see note), scrubbed thoroughly
6cups, packedChinese watercress7 oz., leaves and tender stems; may substitute spinach
Salt
2cupsheavy cream
3-inchpiecelemon grass stalkfinely chopped, inner white part only
2-inchpieceginger rootpeeled and cut crosswise into thin slices
1tspAsian hot saucesuch as Sriracha
1tspfish saucesuch as Tiparos brand
1largescallionwhite and light-green parts, finely chopped (1/4 cup)
6large sprigscilantrofinely chopped, leaves and stems
black pepperfreshly ground, optional
Instructions
Prepare a bed of crumpled aluminum foil or rock salt on a rimmed baking sheet for the oysters to nest in so they won't tip over as they roast.
Shuck the oysters, using an oyster knife to separate them from their shells and leaving them in their half-shells. Arrange them on the baking sheet. Cover loosely with damp paper towels and refrigerate (up to a few hours in advance).
When you are ready to cook the oysters, preheat the oven to 500 degrees.
Blanch the watercress or spinach in a large pot of salted boiling water for about 2 minutes, until it has wilted but is still bright green. Drain and rinse in cold water until completely cooled, then drain again and squeeze to remove as much excess moisture as possible. Chop the greens.
Combine the cream, lemon grass, ginger, hot sauce and fish sauce in a large, heavy-bottomed saucepan over medium-high heat. Bring to a boil, then reduce the heat to medium and cook for about 25 minutes, to reduce the total amount to 1 1/4 cups. Strain the cream into a separate saucepan, discarding the solids.
Add the chopped greens, scallion and cilantro. Taste and add salt and/or pepper as needed. Cook for about 2 minutes to warm the greens through, then reduce the heat to low to keep the mixture warm.
Create a bed of rock salt about 1 inch thick on individual plates.
Roast the oysters on the baking sheet on the lowest rack of the oven for 10 to 15 minutes, until their juices are bubbling and the edges of the oysters begin to curl.
Use a towel to transfer 4 of the oysters and their half-shells (the shells will be hot) to each plate. Spoon a heaping tablespoon of the greens mixture onto each oyster. Serve immediately. (Depending on the size of the oysters you use, there might be some cress left over.)
Notes
Taste one of the oysters that you will be using to check the salinity level, then adjust the salt in the cress mixture accordingly. The idea is to spoon the cress mixture onto the oyster and let it meld with the oyster's liquor. Remember that the seasoning of the cress must be concentrated, because it will become diluted when it mixes with the liquor. If you can't find Chinese watercress, usually available at Asian markets, use baby spinach instead. Do not use English watercress; the stems are not delicate enough.You'll need enough rock salt to create a 1/2-inch thick bed on each dinner plate; this will hold the hot half-shells. The salt should be discarded after the meal is done.Make Ahead: The cress mixture can be refrigerated for up to 1 day and reheated. The oysters can be opened a few hours before you plan to use them. Set them in the aluminum foil bed as described in the directions below; cover them loosely with damp paper towels and refrigerate until ready to roast.Photo Credit: Bill O'Leary/The Washington Post