The best time to eat roasted nuts is immediately after they have been taken from the wok. Once cool, they are no longer as sweet or fragrant although the taste partly returns after reheating.

But be careful if you use a microwave as the nuts can easily explode.

Chinese chestnuts differ from one region to another with weather and geographic conditions the primary factors affecting quality.

Chestnuts grow widely in mountain areas with the smaller, tastier variety produced in parts of northern China such as Hebei Province and suburban Beijing being the most popular.

Sweet potatoes

Mostly grown by the vendors themselves, the baked snack is especially welcomed on cold winter days.

Vendors usually wheel around a modified barrel oven filled with coal which slowly roasts the sweet potatoes inside. When ready, the potatoes are showcased on top of the iron bin, and are typically sold by weight.

According to traditional Chinese medicine, sweet potatoes are good winter food as they help the body remove the season's dryness.

Also sweet potatoes rank highest in nutritional value when considering fiber content, complex carbohydrates, protein, vitamins A and C, iron, and calcium.

When it comes to choosing the best sweet potato, look for those that are soft and have a wrinkly skin. A finger check usually does the trick, too.

If the potato gives under the weight of your finger, then it is usually sweeter and more moist, the soft texture due to the potato's high sugar content.

The vendor will then weigh the potato and place it in a thin plastic bag.

Be careful though as the potato may still be hot although Shanghainese actually love to warm their hands on the bag first anyway.