Pat the 6 chicken thighs dry with paper towels. Season both sides of each thigh with kosher salt and freshly ground black pepper.
Heat 1 tablespoon olive oil in a large cast-iron skillet over medium-high heat until shimmering. Carefully add the chicken thighs to the skillet skin-side down (hot oil may splatter).
Cook the chicken until the skin is golden and crisp, about 4 to 5 minutes, then flip and cook the other side about 4 to 5 minutes. Transfer the chicken to a plate.
Drain off all but 1 tablespoon of fat from the skillet. Add the 1 small finely chopped onion and 4 minced garlic cloves, stirring and scraping the bottom of the pan to release browned bits. Cook, stirring frequently, until the onion is soft, about 3 minutes.
Stir in 2 tablespoons tomato paste and cook, stirring, for 1 minute.
Add the drained and rinsed chickpeas (2 15-ounce cans), 1/4 cup harissa, and 1/2 cup chicken stock to the skillet. Stir to combine and bring the mixture to a simmer.
Nestle the chicken thighs back into the chickpea mixture, skin-side up.
Transfer the skillet to the preheated oven and roast until the chicken is cooked through, 20–25 minutes. Remove from the oven and let the chicken rest briefly before serving.
Notes
Harissa: learn how to make your own here!
Chicken stock: homemade recipe here!