Line a baking sheet with foil and spray with olive oil cooking spray; set aside. Rinse tenderloin under cold water and pat dry with paper towels. Cut into 4 servings. Use a pastry brush to brush 1/4 cup mustard on pork loin. Sprinkle tenderloin pieces with 2 tablespoons of the herbs. Place on prepared baking sheet. Roast in preheated oven for 18 to 20 minutes. In a small saucepan over medium heat, combine chicken broth and pearl onions. Reduce liquid by half and add remaining 1/4 cup mustard and 1 tablespoon fines herbs. Heat thoroughly. Serve roasted tenderloins hot with onions and sauce.