FOR THE PASTRY LIDS
150 grams all-purpose flour (about 1 cup), plus more for dusting
8 tablespoons (1 stick) cold unsalted butter, cut in 1/4-inch cubes
1 egg yolk
1 tablespoon half-and-half
FOR THE STEW
2 lobsters, about 1 1/2 pounds each, or 12 ounces lightly cooked lobster meat
3 tablespoons butter
1/3 cup finely diced celery
1 cup finely diced leek
Salt and pepper
1/8 teaspoon cayenne pepper
1 teaspoon chopped thyme leaves
1/2 teaspoon grated lemon zest
1 cup half-and-half
2 teaspoons potato starch dissolved in 2 tablespoons cold water
1/4 cup cup crème fraîche
FOR THE GARNISH
1 tablespoon chopped parsley
1 tablespoon chopped tarragon or dill
1 tablespoon chives, cut very small
2 tablespoons chopped celery leaves, from interior stalks
Make the pastry lids: Put the flour and a pinch salt in a mixing bowl. With fingers, work half the butter (4 tablespoons) into the flour until completely incorporated. Add the remaining butter, leaving it in small chunks. Quickly stir in 1/4 cup ice water to form a somewhat sticky ball. Knead together briefly, wrap in plastic, and press to make a flat disk about 1-inch thick. Refrigerate overnight or for at least an hour.
When ready to cook, heat the oven to 400 degrees. Roll the dough on a lightly floured surface to a diameter of about 12 1/2 inches. Using an inverted bowl as a guide, cut two 6-inch diameter circles. (The remaining dough can be rerolled and saved for another purpose.)
Mix egg yolk and half- and-half. Place the circles on a parchment-lined baking sheet and paint lightly with the egg yolk mixture. Bake for 10 minutes at 400 degrees, then lower the temperature to 350 degrees and continue baking until nicely browned, about 10 minutes. (May be baked ahead, if desired, and reheated.)
Make the stew: Place the lobsters in a large pot of rapidly boiling water over high heat. Cook for 6 minutes, then remove them and cool in a large bowl of cold water. Take the meat from the claws, tail and knuckles. (Discard the shells or use them for lobster stock.) Then cut the meat into roughly 1/2-inch chunks and set aside.
Melt the butter in a wide, heavy skillet over medium heat. Add the celery and leek, season with salt and pepper, stir and cook until softened, 3 to 4 minutes. Add the lobster meat, cayenne, thyme and lemon zest and stir together.
Pour in the half-and-half and simmer for 2 minutes. Add the potato starch mixture and cook until thickened, about 1 minute. Check the seasoning and adjust, then stir in the creme fraiche.
Assemble the dish: Spoon the hot lobster stew into 2 deep bowls. Place a baked pastry lid on each. Sprinkle with the chopped parsley, tarragon, chives and celery leaves, and serve immediately.