There are several locations but I like the one in Old Chinatown (Broadview and Gerrard), which has some neat guys serving. They have a variety of the standard Vietnamese dishes. Coffee with condensed milk over ice for the warm days, Pho Tai (noodle soup with thinly sliced raw beef) for the cold ones.
What makes this little Northern Vietnamese restaurant's so special is the signature dish, grouper vermicelli. I am not a big fish eater, typically I prefer to order meat dishes, but this fish is magical. The grouper is lightly dusted with flour, dill and curry (I think) and then fried so the edges are crispy. This is served on a bed of vermicelli noodles, shredded lettuce, cilantro and peanuts. You can add sauce or just eat it the way it is. I love this fish! I have also tried the grouper as a soup and it is equally good. Other standout dishes for me are the beef sate with basil and mint and calamari patties.