Many restaurants and street food vendors in Hanoi serve a single dish. You walk up, tell them how many people will be eating and take a seat while they assemble everything. This is bun bo nam bo, a bowl overflowing with vermicelli noodles, marinated beef, bean sprouts, green papaya, peanuts, garlic chips, dried onions, fish sauce and probably half a dozen other ingredients. You mix it all up before digging in. Each bowl costs about $3.