Mix the garlic, ginger, lemon grass,
coriander, Nuoc Mam sauce, if used and sesame oil.
Marinate the mushrooms in the mixture for
3-4 hours, turning frequently.
Make the dipping sauce by mixing and
pounding all the dipping sauce ingredients together except for the
coconut milk. A rough paste should result. Stir in the coconut milk.
Thread the mushrooms onto four skewers.
Place on the barbecue or under a preheated high grill for about 3
minutes on either side, basting with the marinade.