o For the crust:
Scant 1 teaspoon (4 grams) fine sea salt
2 1/2 cups flour, plus more for the work surface
3 tablespoons warm water
1/2 cup plus 2 tablespoons unsalted butter, melted, plus more for greasing the ring molds
3 large egg yolks
o For the filling:
1/2 stalk lemon grass, thinly sliced
1 teaspoon coriander seed
1/2 cup whole milk
1 tablespoon unsalted butter
1 large leek (white parts only), cleaned and finely chopped ( 1/2 cup)
Fine sea salt
8 to 12 asparagus spears (woody ends trimmed off), cut into 1-inch pieces
3 large eggs, plus 1 large egg yolk
1/4 cup heavy cream
2 tablespoons plain whole-milk yogurt
1/4 teaspoon mild curry powder
Freshly ground black pepper
About 1 ounce ( 1/4 cup) crumbled feta cheese
1 1/2 ounces ( 1/2 cup) freshly grated Gruyere cheese
1 tablespoon finely chopped flat-leaf parsley
For the crust: Combine the sea salt and flour in the bowl of a stand mixer or handheld electric mixer; beat on low speed to blend.
Stir together the water, melted butter and egg yolks in a liquid measuring cup.
Beating on low speed, add the water mixture in three additions to form a rough dough that holds together. Wrap the dough in plastic wrap; refrigerate for at least 1 hour and up to 1 day.
Lightly flour a work surface. Divide the dough in half; roll out each half on the work surface to an 8-by-12-inch rectangle. Reserve one for later use (see headnote); transfer the remaining rectangle of dough to a flexible cutting board and refrigerate for 20 minutes.
Preheat the oven to 350 degrees. Line a baking sheet with parchment paper or a silicone liner. Use a little butter to grease the ring molds, then arrange them on the baking sheet.