For the dough: In the bowl of a food processor fitted with the metal blade, combine the flour, salt and pepper; pulse to mix. Add
the butter and pulse until mixture resembles coarse meal. With the machine running, add the ice water through the feed tube in a slow, steady stream, just until the dough holds together without being too wet. Do not process more than 30 seconds. Turn out the dough onto a clean work surface, shape into a flattened disk, wrap in plastic, and refrigerate at least 1 hour or overnight.

Preheat the oven to 350°. Divide dough into 8 equal pieces. On a lightly floured work surface, roll each piece of dough into a 4¾-inch round, ⅛-inch thick. Fit dough rounds into 8 (4-inch) tart pans with removable bottom, pressing into edges. Line shells with parchment, leaving a 1-inch overhang and fill with pie weights. Place pans on a baking sheet and bake until edges are just beginning to turn light brown, 18 to 20 minutes. Remove the parchment and weights, and bake until golden, 3 to 5 minutes more. Transfer pans to a wire rack to cool completely.

For the filling: Coat a medium skillet with oil and heat over medium heat. Add the asparagus, onion, ½ cup water, and a pinch of salt. Bring to a simmer and cook, stirring occasionally, until asparagus is crisp-tender, about 5 minutes. Drain any water from the pan, transfer mixture to a plate and cool completely.

In a medium bowl, whisk together the yogurt, egg yolks, cheese, and pinch of salt and pepper just until smooth. Stir in asparagus mixture.

To assemble the quiche: Reduce oven temperature to 325°. Fill the tart shells with the asparagus mixture and place on a baking sheet. Bake, rotating pan halfway through, until the filling is puffed and set, 18 to 20 minutes. Serve warm.