Heat a grill to medium heat.
In a small saucepan, add the vegetable oil, sliced garlic chives and bring to the simmer. Stir, then take the pan off the heat and transfer the garlic chive oil to a bowl.
Thread each prawn onto a skewer (tail through the top of the head) and char grill on medium heat for 2 minutes on each side, or until cooked.
While the prawns are grilling, place the vermicelli noodle on a plate and reheat it in the microwave for 1 minute on high. Now coat the noodles with the garlic chive oil and sprinkle with the crushed peanuts. Tear a piece of the noodles and wrap around the grilled prawn, remove the skewer. Place the wrapped prawn on the lettuce, then add the mango, banana, and cucumber and roll up.
Repeat this process and dip the wraps into nuoc mam cham dipping fish sauce.