Preheat oven to 375. Place pork on rack in shallow baking pan. Insert meat thermometer into thickest part of tenderloin. Roast, uncovered, 25 to 30 minutes, or until thermometer registers 159°F Let stand, covered 5 to 10 minutes while preparing sauce.
Cook and stir mushrooms, green onion and garlic in butter in small saucepan over medium heat until vegetables are tender. Stir in cornstarch, parsley, thyme and pepper. Stir in water, sherry and bouillon grandules.
Cook and stir until sauce boils and thickens. Cook and stir 2 minutes more. Slice pork and serve with sauce.
*Shitake mushrooms can be used in place of the regular mushrooms.