Describe a food people eat on special occasions.

I'd like to describe bánh chưng, a square sticky rice cake that practically every family in Vietnam eats at Tết, the Lunar New Year.

It looks quite plain from the outside — a green parcel tied up with bamboo string — but there's a lot inside. You've got a layer of sticky rice, then mung bean paste, then fatty pork seasoned with pepper, and then the same layers again in reverse. The whole thing is wrapped in large green leaves, which give the rice its colour and a slightly earthy smell.

Making it takes most of a day. The rice and beans are soaked overnight, and the next morning the family sits on the floor together to wrap the cakes, which is harder than it looks if you want neat corners. After that they're boiled in an enormous pot for ten or twelve hours, so somebody has to stay up and keep the fire going. When I was little, that was the best part, because the children were allowed to stay awake and listen to the adults telling stories.

As for why we eat it at New Year, there's an old legend about a prince who offered this cake to his father, the king, with the square shape standing for the earth. But I think the real reason today is simpler. It's a dish you can't easily make alone, so it brings three generations into one room. These days plenty of people just buy one from a shop, and it tastes fine, but it isn't quite the same.