Pat the chicken thighs dry with paper towels. Season both sides with kosher salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat until shimmering.
Place the chicken thighs skin-side down in the skillet. Cook without moving for 7 to 8 minutes until the skin is golden brown and crispy.
Flip the chicken thighs and cook for an additional 7 minutes on the other side until browned.
Remove the chicken thighs from the skillet and set aside on a plate.
Reduce the heat to medium. Add the minced garlic to the skillet and sauté for 30 seconds until fragrant, stirring constantly to avoid burning.
Stir in the Dijon mustard, chicken broth, lemon juice, and dried thyme. Scrape the bottom of the skillet with a wooden spoon to loosen any browned bits.
Return the chicken thighs to the skillet, skin-side up. Spoon some sauce over the chicken.
Cover the skillet and simmer for 8 to 10 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
Remove the chicken thighs from the skillet and place on a serving plate.
Stir the butter into the sauce in the skillet until melted and smooth.
Pour the sauce over the chicken thighs and garnish with chopped fresh parsley before serving.