In a mixing bowl, combine white sugar, fish sauce, rice wine vinegar, lime juice, water, minced chilis, and garlic for the Nuoc Cham sauce. Stir well and let it sit for at least 10 minutes.

Bring water to a boil in a pot and add vermicelli noodles. Soak for 5-7 minutes until tender. Drain and rinse with cold water.

In a large mixing bowl, combine pork mince, fish sauce, sugar, chopped green onions, minced garlic, white pepper, salt, and optional lemongrass. Mix thoroughly and form into golf ball-sized patties.

Heat a skillet over medium-high heat with oil. Fry meatballs for 2-3 minutes on each side until golden brown.

In serving bowls, layer the prepared vermicelli noodles, place meatballs over the noodles, top with fresh vegetables, and drizzle with Nuoc Cham sauce.