01 - Preheat the oven to 400°F. Lightly grease a baking dish large enough to hold the chicken breasts in a single layer.
02 - In a mixing bowl, whisk together the Dijon mustard, whole grain mustard, honey, olive oil, apple cider vinegar, minced garlic, thyme, salt, and pepper until well combined and smooth.
03 - Arrange the chicken breasts in the prepared baking dish. Pour the honey mustard sauce evenly over the chicken, turning each breast to coat thoroughly on all sides.
04 - Bake for 30 to 35 minutes, or until the chicken reaches an internal temperature of 165°F and the sauce has thickened slightly.
05 - For a golden caramelized finish, switch the oven to broil and cook for an additional 2 to 3 minutes, watching carefully to prevent burning.
06 - Remove the baking dish from the oven and let the chicken rest for 5 minutes. Garnish with chopped fresh parsley and serve with lemon wedges alongside roasted vegetables, steamed rice, or a crisp green salad.