Northern Vietnamese cuisine is much harder to find in the U.S.. Most of the immigrants are from the South or Northern descent but transplanted to the South, therefore, finding authentic Nothern Vietnamese cuisine here almost non-existent. IMO, Northern style is more restraint and subtle in their flavorings, which does not appeal to the masses as well. More austere, when you consider the herbs and vegetables that the South adds to their dishes due to availability. Kind of like French wines and other sytle of New World wines (e.g. American, South American, Australian, etc.), but you are paid back in other qualities in exchange for the exuberance up front. **Ducking in case something is aimed at me for that comment.**
If you tasted the real thing in Hanoi unlike other dishes that translate well in foreign land, this dish doesn't, because the ingredients are actually quite simple in its beauty. it's the preparation and balance of flavor that is key. Here are the basic and essential aspect to Bun Cha Ha Noi that makes all the difference:
1. Quality of meat due to its origin - Meat in Vietnam is still free range, because they haven't commercialize nor mass produced it yet. Not to mention all of the other aspects, such as variety, etc.
2. Charcoal - There is nothing like real wood charcoal. Also, the wood that is indigenous to the region. Tending the fire just perfectly for that charring of the meats.
3. Cut of meats - They tend to use pork belly in Vietnam which is much leaner than in the US. Shoulder meat is usually the cut, which is way too lean for that fatty charred goodness.
4. Seasoning and marinating the meat - The ingredients are simple, but it's the restraint and balance that is the true art.
There are some restaurants in the US where I've experienced that Northern cuisine flavor profile: Le Colonial and Slanted Door in SF (on non-fusion dish in the early years).
In Paris, there is more of a Northern Vietnamese cuisine due to the closer ties and history with the French for various reasons.
“Nothing is more agreeable to look at than a gourmande in full battle dress.”
Jean-Antheleme Brillat-Savarin (1755-1826)