Sprinkle the chicken thighs with kosher salt and pepper.
Heat the oil in a large, heavy, oven-safe skillet (cast iron is perfect) over medium-high heat.
When the oil is hot, but not smoking, arrange the chicken thighs in the skillet, skin-side down. Cook for 15 mins, or until the skin is well browned, moving the thighs from time to time to make sure they are browning evenly. Do not turn them over.
Move the skillet to the oven and continue cooking, skin-side down, for another 15 min. Turn them over and continue cooking for 5 min longer.
To test for doneness, insert a food thermometer into the thickest part of a thigh. The minimum safe temperature for chicken and other poultry is 165°. Serves 6