Make the Thyme garlic Butter first: In a small bowl, mix the stick of butter,garlic, thyme and salt(if using) until combined. Set aside.
Preheat the oven to 475°F. s. Season the chicken with salt and pepper.
Heat the oil over high heat in a 12 inch cast iron skillet or other oven-safe frying pan. As the oil is heating, add the butter to the skillet. The pan is ready when the oil is hot, but not smoking.
Add the thighs to the skillet, skin side down. Cook for 2 minutes. Reduce the heat to medium high and continue cooking the chicken for about 10 more minutes. Move chicken around and rotate the pan so heat to the chicken is distributed evenly.
Transfer the skillet to the preheated oven and continue cooking for 5 minutes more. Turn the chicken thighs over in the pan and continue cooking for an additional 10-13 minutes or until chicken is fully cooked to 165°F on an internal meat thermometer.
Remove the chicken from the oven and let sit for a few minutes. Top each chicken thigh with a tablespoon of Thyme Garlic Butter before serving.
For flexibility and control, I use unsalted butter for all of my cooking.I like the flavor of frying food in a mixture of oil and butter. If you prefer, the butter can be omitted.