Bun cha is a must eat when in Hanoi. There are many places that boast the "best" bun cha in the city, but Bun Cha Ta has my vote.
The restaurant is much more modern (read clean/hygienic) than the typical mom-and-pop shop, which is good for Westerns not used to Southeast Asian street food standards.
The servers were all very nice and for the most part spoke English well. The menu also has English on it.
There are a few options for bun cha, but for the true experience get the original bun cha meal with fried egg rolls.
Come hungry because it can be a lot of food.
Good for breakfast, lunch, or dinner.