Grilled Lemongrass Pork Tenderloin Skewers: Suon Nuong Xa

Name: Grilled Lemongrass Pork Tenderloin Skewers: Suon Nuong Xa
Ingredients: 1/4 cup fish sauce; 1 tablespoon soy sauce; 3 tablespoons sugar; 2 tablespoons vegetable oil; 2 stalks lemongrass, outer leaves and tops removed, root ends trimmed, and stalks finely grated; 1 large shallot, finely chopped; 2 large cloves garlic, finely chopped; 1 pound pork tenderloin, thinly sliced; 16 bamboo skewers, soaked for 20 minutes and drained; Rice vermicelli, cooked, for serving; 1/2 cup chopped unsalted roasted peanuts; Nuoc cham, as needed, recipe follows; 5 tablespoons sugar; 3 tablespoons water; 1/3 cup fish sauce; 1/2 cup lime or lemon juice; 1 large clove garlic, minced; 1 or more bird's eye or Thai chiles, seeded and minced; 1 shallot, peeled, thinly sliced, and rinsed (optional)