Preheat oven to 350 degrees F. Spray a large, shallow baking dish with cooking spray.
Place sliced onion in the bottom of the prepared dish.
Season chicken with salt and pepper to taste and place on top of the onion. Add fresh herbs to the dish.
In a large bowl or measuring cup, whisk together beef broth, olive oil, Dijon mustard, honey, sherry, Worcestershire sauce, dry soup mix, and salt until completely combined.
Pour sauce over chicken.
Bake, uncovered, for about 45-55 minutes (or until chicken is cooked through and reaches an internal temperature of 165 degrees F). The cooking time will vary depending on the size and thickness of your chicken. Baste with pan sauce and garnish with additional fresh herbs, just before serving.
Serve with cheese toast.