01 - Preheat oven to 400°F. Lightly grease a 9x13 inch baking dish or similar shallow pan that will accommodate the chicken in a single layer.
02 - In a medium bowl, whisk together Dijon mustard, whole grain mustard, honey, olive oil, lemon juice, minced garlic, smoked paprika, dried thyme, salt, and black pepper until fully incorporated and smooth.
03 - Arrange chicken breasts in the prepared baking dish. Pour the honey mustard sauce evenly over the chicken, turning each piece to ensure thorough coating on all sides.
04 - Bake uncovered for 30 to 35 minutes, or until the chicken reaches an internal temperature of 165°F and the sauce is bubbling with slight caramelization around the edges.
05 - For enhanced color and caramelization, switch the oven to broil on high for 2 to 3 minutes. Watch closely to prevent burning the sauce.
06 - Remove from the oven and let the chicken rest for 5 minutes to allow juices to redistribute. Spoon the remaining sauce over each piece and garnish with fresh chopped parsley before serving.