Place a 12-inch cast iron skillet over medium heat. Add a tablespoon of olive oil to the skillet. Add the onion and garlic and cook for 2 minutes until soft. Add the chickpeas, tomatoes, chicken stock, thyme and 1 teaspoon of the harissa spice mix. Stir to combine and bring to a simmer.
Trim any excess fat off the chicken thighs, using kitchen shears. Season the chicken with the harissa spice, salt and pepper. Tuck the chicken thighs, skin side up into the chickpeas. Drizzle the top with a couple tablespoons of olive oil.
Bake, uncovered for 45 minutes, until the chicken is cooked through. Scatter the red peppers over the top and return to the oven for 5 minutes.
