Potato Leek Pie
For the crust
For the filling
  1. To make the crust, combine the flour and salt in a food processor. Cut the cream cheese and butter into large cubes and add them to the flour. Pulse to break up the cubes into smaller pea-size pellets.
  2. Drizzle in the water and vinegar through the feeding chute and continue to pulse the machine until the dough comes together into a fairly cohesive ball. It will still be a bit loose. Scrape the dough onto a clean cutting board or counter. Gather the clumps into a tight ball, compressing it. Do not knead it, as you do not want to form a lot of gluten, which will make the crust chewy. Pat it down into a disk about 1 inch thick. Wrap the dough in plastic wrap and refrigerate it while you make the filling.
  3. Fill 2 medium-size bowls three-quarters full with cold water. Lay out two piles of paper towels on the counter, for drying the potatoes and leeks.
  4. To make the filling, peel the potatoes, give them a good rinse under cold running water, and cut them into 1/2-inch cubes. Submerge the cubes in one of the bowls of water.
  5. Cut the leeks in half lengthwise and thinly slice them crosswise. Dunk them in the other bowl of water. Leeks are inherently muddy, so you will need to wash them a few times. (Trust me when I say grittiness is not a desired texture in this pie.) Scoop the leeks out of the water into a colander, and dump the water out of the bowl. You will notice the bottom of the bowl is muddied from the leeks; rinse out that mud. Drop the leeks back into the bowl and fill it up again with cold water. Repeat the dunk, rinse, scoop, and dump a few times until the water is clear when the leeks have been removed. Drain the leeks in the colander and pat them dry with one set of paper towels. (Alternatively, you can spin them dry in a salad spinner.)
  6. Drain the potatoes in the colander and give the colander a good shake or two to rid the potatoes of excess water. Pat the potatoes dry with the other set of paper towels.
  7. Melt the butter in a Dutch oven or large skillet over medium heat. Once the butter starts to foam, add the leeks and stir-fry them until they soften up a bit, 5 to 7 minutes. Stir in the potatoes, cover the pan, and cook the potatoes and leeks, stirring occasionally, until they are barely tender, 8 to 10 minutes. Stir in the thyme, salt, and peppercorns and remove the pan from the heat.
  8. Position a rack in the center of the oven and preheat the oven to 400°F.
  9. Lightly flour a clean countertop. Roll out the crust to a 12-inch circle. Keep dusting the crust lightly with flour as needed to ensure a stick-free crust. Place the rolled-out crust in a 9-inch pie plate, pressing it gently against the bottom and sides. Flute the edge by lifting a bit of the rim of the crust and pinching it between your thumb and forefinger; do this all around the edge. Alternatively, press the tines of a fork into the dough all around the edge to create ridges.
  10. Stir the shredded cheese into the potato-leek filling. Spoon and spread this into the prepared crust. Place the pie on a cookie sheet to catch any dripping fat from the crust. Bake the pie until the crust at the edge is crispy brown and the potatoes and leeks in the filling have a well-tanned appearance, 30 to 40 minutes.
  11. Transfer the pie plate to a wire rack and allow the pie to cool for 15 minutes before slicing it into wedges and serving with the sauce.