Preheat the oven to 400°F.
Wash and pat dry chicken thighs. Place them in a large baking dish and season with salt and pepper. Allow them to marinate for 30 minutes to enhance juiciness.
In a small bowl, mix garlic, thyme, olive oil, and butter together.
Rub the chicken thighs with the mixture.
Place thyme sprigs around the thighs and transfer them to the oven.
Bake for 40 minutes, basting with pan juices halfway through cooking.
Remove from the oven and serve with mashed potatoes, drizzled with the pan juices.