In a container, combine meat, onion, garlic, broth and rosemary. Marinade in refrigerator 6 to 8 hours.
Drain pork tenderloin and let sit at room temperature 10 minutes. Set aside 60 mL (¼ cup) broth and rosemary sprigs, then discard remaining marinade.
Finely grind dried mushrooms.
Baste pork tenderloin using Canton Dijonnaise sauce and dredge in mushroom powder.
Preheat barbecue on High.
In the middle of a sheet of double-layer aluminum foil, spread leek and place meat on top. Bring up all 4 corners to make a bowl. Add reserved marinade, rosemary sprigs and white mushrooms, then season with pepper.
Close foil packet and place on hot barbecue grill. Reduce heat to Medium. Cook 20 minutes.
Slice pork and serve with vegetables.
