Preheat your oven to 400°F (200°C). Line a large baking dish or a rimmed baking sheet with parchment paper or aluminum foil. This prevents the honey from sticking to the pan and makes cleanup much easier later on.
In a medium-sized mixing bowl, whisk together the Dijon mustard, honey, whole grain mustard, olive oil, minced garlic, dried thyme, salt, and black pepper. Stir until the mixture is completely smooth and the honey is well incorporated with the mustard.
Pat the chicken thighs dry with paper towels to ensure the sauce sticks better. Place the chicken thighs in the prepared baking dish. Pour the honey mustard mixture over the chicken, using a brush or spoons to ensure each piece is generously coated on all sides.
Place the dish in the center rack of the oven and bake for 25 to 30 minutes. Halfway through the cooking time, use a spoon to baste the chicken with the juices and glaze from the bottom of the pan. This helps create a thick, sticky coating.
Ensure the chicken has reached an internal temperature of 165°F (74°C) using a meat thermometer. If you want a more charred look, you can broil the chicken for the last 2 minutes. Let the chicken rest for 5 minutes before serving to lock in the juices.