Step 1: Prepare the Marinade

1. Mix the Marinade Ingredients: In a medium bowl, whisk together the Dijon mustard, honey, minced garlic, olive oil, apple cider vinegar or lemon juice, salt, black pepper, and fresh rosemary or thyme if using. Stir until well combined and smooth.
2. Marinate the Chicken: Place the chicken breasts in a resealable plastic bag or a shallow dish. Pour the marinade over the chicken, making sure each piece is coated. Let it marinate in the refrigerator for at least 15 minutes, or up to 2 hours for more intense flavor.

Step 2: Preheat the Oven

1. Set Oven Temperature: Preheat your oven to 400°F (200°C) and lightly grease a baking dish with a bit of olive oil or non-stick spray to prevent sticking.

Step 3: Bake the Chicken

1. Arrange the Chicken in the Baking Dish: Remove the chicken breasts from the marinade and place them in the prepared baking dish, leaving a little space between each piece. Pour any remaining marinade over the top of the chicken for extra flavor.
2. Bake: Bake in the preheated oven for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the top is golden-brown and caramelized. Basting with the pan juices halfway through cooking enhances the glaze.
3. Broil for Extra Color (Optional): For an extra-crispy top, broil the chicken for 2-3 minutes at the end of baking, keeping a close eye to prevent burning.

Step 4: Garnish and Serve

1. Garnish: Sprinkle fresh parsley or rosemary on top for a pop of color and flavor.
2. Serve: Serve warm with your favorite side dishes, like roasted potatoes, steamed vegetables, or rice.