Serves 4

This remarkably simple and flavorful dish is the item ordered most often at chef Joel Robuchon's restaurant, Jamin. The lamb roasts in a thyme-infused salt crust, which actually serves as a hermetic, flavorful roasting shell. The crust is discarded after cooking.

Salt Crust:
½ cup (150 g) salt
1 cup (240 g) coarse (kosher) salt
1 egg, separated
3¾ cup (525 g) unbleached flour
2 Tbl dried thyme, mixed with 1¼ cups (310 ml) water

4 Lamb:
2 pounds (900 g) boneless roasting lamb (a portion of leg of lamb works well)
Freshly ground black pepper
½ tsp dried thyme
Pinch of salt
1 tsp coarse (kosher) salt

1. Preheat the oven to 400° F (205°C).
2. Prepare the salt crust: in a large bowl, blend together the two salts, the egg white, flour, and thyme and water mixture. Knead until well blended. It is essential that the dough be firm, not too moist or sticky, or the lamb will steam, not roast. If necessary, knead in additional flour for a firm dough. Roll out the dough so it is large enough to wrap the lamb.
3. Season the lamb with the pepper and thyme. Completely wrap the lamb in the salt crust, checking to make sure it is well sealed, and place on a baking sheet. (this can be done several hours ahead of time.)
4. Just before roasting, combine the egg yolk with the pinch of salt and ½ tsp water and, with a pastry brush, brush the mixture over the surface of the crust. Sprinkle all over with coarse salt.
5. Place the lamb on a baking sheet in the oven and roast for 25 to 30 minutes for rare (or until the interior of the lamb is cooked to 112°F, or 45°C, when measured with a meat thermometer). For well-done lamb, cook an additional 5 or 10 minutes. The crust should be a deep, golden brown. Let the lamb rest in the crust for 1 hour before serving. (The lamb will remain warm.)
6. To serve, cut open the crust at one end, remove the lamb, and cut the meat on the diagonal, into very fine slices. Discard the crust. Serve with buttered fresh pasta or a potato gratin.