Step 1

In a large bowl, mix together the harissa, 3 tablespoons of the olive oil, cumin, 2 1/2 teaspoons of the salt, and 1/2 teaspoon of the black pepper. Add the chicken and potatoes, then rub the thighs and legs and potatoes with the marinade. Be sure to use your hands to rub the sauce under the skin of the chicken. Let stand for 30 minutes at room temperature.

Step 2

In a medium bowl, toss the leeks together with the lemon zest, 1/4 of the salt, and the remaining 1 1/2 tablespoons of olive oil.

Step 3

Preheat the oven to 425ºF (220ºC). Adjust the oven rack to the center of the oven.

Step 4

Transfer the chicken and potatoes, and any sauce in the bowl, onto a large rimmed baking sheet. Arrange the chicken pieces so they are skin side up, and make sure the chicken parts and potatoes are in a single layer. Bake for 20 minutes.

Step 5

Remove the baking sheet from the oven. Toss the potatoes (so they can brown on the other sides of them) then strew the leeks over everything on the baking sheet. It may look like a lot, but they'll bake down.

Step 6

Bake until the chicken is cooked through, another 20 to 25 minutes. While the chicken is cooking, in a small bowl, mix the yogurt with the garlic, the remaining salt and pepper, and a squeeze of fresh lemon or lime juice.

Step 7

Remove the baking sheet from the oven and spoon the yogurt sauce in various places over the chicken and potatoes. Top with fresh herbs and serve.