There are many specialised jiaozi restaurants both in China and Taiwan. Shanghai is famous for its Jiazi yet it doesn't quite suit foreigners taste for the simple reason that it's always much too oily, but the locals seem to like it. In most cases it's best served boiled. Shredded ginger in vinegar/soy sauce is often served as a dip sauce. Not particularly Southeast Asian, this popular Chinese dish is available in many Chinese restaurants in the region and it's becoming a rather popular snack.