From Charlie's Practical Guide to the New American Kitchen
3/4 c mirin (sweet Japanese rice wine)
1/2 c rice wine vinegar
2 T extra virgin olive oil
2 T shallots, minced
1 green apple, unpeeled
1/2 English cucumber, halved lengthwise, seeded
24 oysters, scrubbed clean
Kosher salt or crushed ice
optional whole spices, peppercorns, star anise, coriander seeds
Opening an oyster is something that must be done carefully with an oyster knife, preferably one with a stainless steel blade and a textured handle for a nonslip grip. An oyster shell is in two parts: one cupped to hold the body and the other relatively flat, like a lid. Using a folded kitchen towel, securely hold the oyster on a stable work surface, cup side down with the point (or hinge side) facing towards you. Insert the tip of the oyster knife through the hinge and turn your hand (like you are turning an ignition key) until you hear the hinge pop. Give a full twist to scrape the blade across the top of the shell cutting the muscle that attaches the oyster. Then cut the bottom muscle, keeping your hand out of the way and the oyster level at all times (so you don't lose any of the juice).
Whisk together the Mirin, vinegar, oil, and shallot in a medium bowl. Julienne the apple and cucumber, then dice them fine. Immediately drop them into the Mirin mixture (the acid in the wine will keep the apple from turning brown).
This can be done several hours before serving, but oysters are best when freshest. It's preferable to make the dressing, assemble the serving plates, and open the oysters at the last minute.
Get out a sheet pan. Take a piece of aluminum foil twice the length of the pan and crinkle it up to fit the pan and create a contoured bed for the opened oysters: You want them to stay level so the liquid doesn't tip out of the shells. Open the oysters and nestle them into the foil. Cover loosely with plastic wrap and refrigerate.
On each appetizer plate form a mound of salt or crushed ice then flatten it slightly. Spoon the dressing over the oysters while they are still on the pan and then carefully transfer them to the plates, arranging 6 oysters on each. Serve with cocktail forks.