Step 1

Pat the lamb dry; season with salt and pepper.

Step 2

In a large Dutch oven over medium heat, warm the neutral oil. Working in batches if needed, cook the lamb for 1 to 2 minutes per side, until well seared. Transfer to a plate.

Step 3

Wipe out the pot, then heat the sesame oil over medium-low. Cook the onions, stirring occasionally, for 4 to 5 minutes, until they start to become translucent and soft. Add the scallions, ginger, and garlic and cook, stirring frequently, for 2 minutes more, until fragrant.

Step 4

Add the sesame seeds and sambal oelek and cook, stirring constantly, for 30 seconds. Return the lamb to the pan and toss well to combine. Add the broth, vinegar, and soy sauce and bring to a simmer over medium heat.

Step 5

Reduce the heat to low and cook, uncovered, for 1 to 1½ hours, until the lamb is tender (it will cook more in the oven later, but it should be nicely tender at this time). Let cool to room temperature.

Step 6

Do Ahead: The filling can be made 2 days ahead. Transfer to an airtight container and store in the refrigerator.

Step 7

Arrange a rack in the lower third of the oven, preferably with a baking steel or stone on it; heat the oven to 375°F/190°C. Place the par-baked crust on a parchment-lined baking sheet.

Step 8

Cut the halved cucumbers into ½-inch/1-centimeter pieces. Working with a few at a time, arrange cut side down and use the side of a knife to smash firmly. Transfer to a colander placed inside a medium bowl. Season with 2 large pinches of salt and toss well to combine. Let drain while the pie bakes, tossing occasionally.

Step 9

Spoon the lamb mixture into the crust and spread in an even layer.

Step 10

Bake the pie (on the steel/stone, if using) for 40 to 45 minutes, until the filling is bubbly and the crust is deeply golden. Let cool for 20 minutes.

Step 11

Pat the cucumbers dry. In a medium bowl, whisk the vinegar, honey, oil, soy sauce, and red pepper flakes; season with salt, then whisk to dissolve the salt. Add the cucumbers and toss to combine.

Step 12

Using a slotted spoon, transfer the cucumbers to the surface of the pie (alternatively, you can serve them alongside). Sprinkle the pie with the sesame seeds, cilantro, and mint.