Heat oven to 425F
Begin by salting the chicken and laying it skin side down in a cold skillet. Arrange the potatoes into the void spaces. Place over medium heat (3.8/6) for 18-25 minutes until the chicken skin browns and releases itself from the pan. This is the most patient part. If the chicken doesn't come off with relative ease using a spatula, leave it cook.
While the chicken is cooking, prepare the leeks. Remove any shriveled outter leaves and slice the leeks lengthwise and wash them under water to remove any sand in the leaves.
Cut the dark green tips off the leeks leaving the light green and white parts. Slice the leeks and add to a bowl
Pick the fronds off the fennel and save them. We'll use them as a garnish later.
Cut the stalks off the fennel and discard.
Thinly slice the first 1/3 of the bulb and add to the leeks. Add the garlic to the leeks as well.
Slice the remaining leeks as thin as possible. If you have a mandolin, now is the time to use it. 1/16 inch slices. Place in another bowl. We'll dress this later as a raw salad on top of the chicken.
When the chicken releases from the pan, turn the heat off, remove the chicken and potatoes to a plate, leaving the rendered fat in the pan.
Add the harissa paste to the pan of hot chicken fat and stir to make a schmaltz.
Put the harissa schmaltz into a small bowl. Add 2 Tbsp of lemon juice and stir.
Return the pan to medium heat, add some olive oil and the leeks, fennel, and garlic. Season with salt and sprinkle the sugar on top. Carmelize the leeks over ~20 min, adding a bit of water if they begin to stick and burn.
When the leeks have cooked down and caramelized, add the chicken and potatoes to the skillet, skin side up. Roast ~10 min until the chicken thighs are cooked (165F). Remove from oven.
Toss the fennel with a little salt, some pepper, 1 Tbsp lemon juice, and a drizzle of olive oil.
Add the fennel salad to the skillet. Drizzle the schmaltz over the chicken and garnish with the fronds and serve at the table in the skillet.
