How to Make It
Heat the broiler or light the grill. In a medium bowl, combine 1 tablespoon of the fish sauce, 1 tablespoon of the sugar, 2 cloves of the garlic, and the oil. Add the chicken, toss, and then thread each strip onto a wooden skewer. Broil or grill the chicken until just done, about 2 minutes per side.
In a small bowl, combine the remaining 4 tablespoons fish sauce, 1 tablespoon sugar, and 1 clove garlic with the red-pepper flakes, vinegar, lime juice, and water. Set this nuoc cham aside.
In a pot of boiling, salted water, cook the vermicelli until just done, about 9 minutes. Add the bean sprouts during the last minute of cooking. Drain, rinse with cold water, and drain thoroughly.
Put the pasta and bean sprouts on a platter and top with the cucumber, herbs, and chicken skewers. Pour the nuoc cham over all and sprinkle with the peanuts.
Asian fish sauce is available at Asian markets and many supermarkets.