Oysters Béarnaise

To prepare the potatoes: Preheat the oven to 350 F. Place a large pot of lightly salted water over high heat, bring to a boil, and cook the potatoes until tender, 10 – 15 minutes. Drain and cut the potatoes in half lengthwise. Scoop out the inside, leaving a 1/2-inch-thick shell. Place the potatoes in the oven for 3 to 4 minutes to dry slightly. Set aside. Leave the oven set at 350 F.

In a large deep saute pan or skillet over medium-high heat, melt 1 tablespoon of the butter and saute the leek and onion, stirring often, until they are tender and most of the juices have evaporated, 10 to 15 minutes. Add the salt, pepper, and remaining 1 tablespoon butter to the pan and cook for 5 minutes. Add the Pernod, warm it, avert your face, and light it with a match. Shake the pan until the flames subside. Add the tarragon and cook for 3 minutes. Spoon some of the leek and onion mixture into each potato shell and top with one of the oysters and a little oyster liquor.

To prepare the bearnaise sauce: In a heavy medium non-aluminum saute pan or skillet, combine the vinegar, wine, shallots, and 2 tablespoons of the tarragon. Bring the mixture to a boil and cook to reduce to 1/4 cup. Remove from heat and let cool.

One at a time, whisk the egg yolks into the vinegar mixture, then return the pan to low heat and, whisking constantly, gradually add the butter to make a thick sauce. Strain the sauce through a fine-meshed sieve into a bowl and add the remaining 1 tablespoon tarragon, salt, and pepper. Keep warm over barely tepid water.

To serve: Bake the potatoes until the oysters inside plump up and their juices have been absorbed by the potatoes, about 5 minutes. Spoon some of the bearnaise sauce over each of the oysters. Place the oyster-filled potatoes on a layer of rock salt in a serving platter, garnish each with some of the prosciutto, and place the tarragon sprigs among the oysters.