There is no phone number or website, but this tiny 'hallway' of an eatery serves the most fantastic food I ate while I was traveling through South East Asia. They serve one dish, Bun Bo, a Vietnamese staple, made with beef, noodles, nuts and mint leaves in a delicious broth. I'm typically a vegetarian, but I gave it up for a taste.
Three women sit in front on the sidewalk cooking up batches of Bun Bo on demand. Hold up your fingers to signal how many bowls you'd like and wait a few minutes at the low picnic tables to be served your steaming hot meal.
If you don't mind a lackluster atmosphere and love a cheap dinner (only 1 US dollar, and maybe 50 cents for a coke), ask your hotel or hostel to direct you towards Nambo Road. You'll eventually find Bun Bo, the roads aren't long, and it's easy to walk everywhere in Hanoi.