Fried Bánh Chưng (Square cake) is so popular now in Hanoi because of the cold and the fact that Tet (lunar New Year) is coming. You can see lots of shops along the street and many ladies hanging around with shoulders baskets, an iron tray on top of a cooker with lots of small square cakes. This is a bit heavy for a snack but it is my favorite.
You should choose the over cooked ones - they are a bit crispy which is good. Add some Soya sauce, sweet chili sauce and some herbs - wow yummy. It's only 3000Vnd, and you don't need to bargain at all :) You also sit down in the shop or on the pavement and it costs exactly the same. This is a really delicious snack but it's not good for vegetarians because there's meat, pepper and beans in the middle of the cake, which is all covered from sticky rice.