Season the thighs on both sides with salt and pepper and preheat the oven to 400F degrees.
Add the turkey thighs, skin side down, to a cold cast iron skillet and heat it slowly to medium low heat. Cook them, undisturbed, for about 5-7 minutes.
Remove from heat and flip the thigh so they are skin side up. Cover loosely with foil and place in the oven for 20 minutes.
While the thighs are roasting, heat the butter, harissa and honey in a small pot until it starts to bubble. Remove from heat.
Reduce the oven temperature to 350F degrees, uncover the turkey, pour on the harissa honey sauce and roast an additional 30-45 minutes, or until the internal temperature has reached 160F degrees.
Don't touch the thighs while they are browning - they will have a better crispy skin if left alone.
Add more or less harissa paste to adjust the spice level if desired.
If the skin starts to brown too much in the oven, re-cover the thighs with foil.
Turkey is safe to eat at 165F degrees. When you take it out at 160F degrees it will continue cooking. This keeps the turkey from drying out.
The recipe can easily be doubled, tripled, etc. for a larger crowd. Just move the turkey from the skillet (you'll probably have to cook them in batches) to a baking dish and follow the same roasting instructions.