- 1/4 cup kosher salt
- 2 (10-ounce) bags fresh spinach, coarse stems discarded
- 2 leeks (white and pale green parts only), quartered lengthwise and thinly sliced crosswise
- 1 tablespoon olive oil
- 3 ounces slab or thick-sliced bacon, cut into 1/4-inch dice
- 1 shallot, quartered lengthwise and thinly sliced crosswise
- 1 garlic clove, minced
- 1 day-old baguette, crust discarded and bread coarsely ground in a food processor (2 cups)
- 2 tablespoons finely chopped fresh chervil
- 2 tablespoons finely chopped fresh chives
- 2 tablespoons finely chopped fresh flat-leaf parsley
- 2 tablespoons finely chopped fresh tarragon
- Finely grated zest and juice of 1 medium lemon
- 3/4 teaspoon fine sea salt, or to taste
- Rounded 1/4 teaspoon white pepper, or to taste
- Pinch of freshly grated nutmeg, or to taste
- 1 stick (1/2 cup) unsalted butter, melted
- About 10 cups rock or kosher salt for baking and serving (3 pounds)
- 40 oysters on the half shell
- Accompaniment: lemon wedges
- Preheat oven to 500°F.
- Bring a 6- to 8-quart pot three-fourths full of water to a boil with kosher salt, then stir in spinach and cook 30 seconds. Transfer with a slotted spoon to a large bowl filled with ice and cold water to stop cooking. Drain spinach and squeeze dry, then finely chop.
- Wash leeks well in a bowl of cold water, then lift out and drain well.
- Heat oil in a 10-inch heavy skillet over moderately high heat until hot but not smoking, then sauté bacon, stirring, until golden and just cooked through (but not crisp), about 3 minutes. Transfer with slotted spoon to paper towels to drain. Add leeks, shallot, and garlic to fat in skillet and cook over low heat, covered, stirring occasionally, until softened, about 8 minutes.
- Toss together leek mixture, spinach, bacon, bread crumbs, herbs, lemon zest and juice, sea salt, white pepper, nutmeg, and butter in a large bowl with a fork.
- Spread 2 to 3 cups rock salt in each of 2 large shallow baking pans and nestle oysters (in shells) in it. Spoon a heaping tablespoon bread-crumb stuffing loosely on top of each oyster. Bake in batches in upper third of oven until golden, about 6 minutes.
- Serve warm oysters in shells on plates lined with rock salt.