Gingko nuts are the seeds of the Chinese gingko tree, and are used in a number of Asian foods, including rice porridge and egg custard. These nuts are rare in North American and European grocery stores, but they may be found in ethnic groceries or harvested from female gingko trees in the fall. For the best flavor, look for packaged nuts still in their smooth pale shells without significant cracks. The nutmeats should be cream-colored with a papery brown coating, and you can also pick your own fruit, though it has an unpleasant smell. Boiling or roasting gingko nuts is common, since they contain a poison when uncooked.
The gingko tree is also called the ginkgo or maidenhair tree, and is originally native to mountainous areas of China, though the remains of ancestors of this “living fossil” can be found worldwide. The trees are either male or female, with male plants producing cones and female plants producing a malodorous fruit containing the gingko seed. Most cities do not plant female trees, due to their smell.
Look for gingko nuts in Chinese, Japanese, and southeast Asian grocery stores, where they are sold both shelled and unshelled. While pre-shelled nuts are far more convenient than the unshelled variety, they provide a weaker flavor. The shells should be largely unbroken, light tan to cream in color, and smooth, with a cream nut covered in delicate brown skin hidden inside.
Fresh nuts are even more flavorful, but the process of removing them from the fruit can be smelly and difficult. If you choose to pick fresh ginkgo fruits, look for soft, berry-like fruits about the size of a large cherry with a light orange skin and creamy orange pulp. This fruit smells extremely unpleasant, and the odor can cling to your fingers for long periods of time, so wear gloves to protect you during the mid-autumn harvest. Remove the seeds from the pulp and wash them thoroughly, and then prepare the nuts the same way that you would the packaged type.
Ripe gingko nuts must be cooked before you can eat them since they contain a poison that can cause convulsions if consumed in large quantities. This poison is destroyed by heat, such as that produced by roasting gingko nuts in oil, pouring boiling water over them, or cooking them in porridge or pudding. Roasting or boiling the nuts has the added benefit of cracking the shells, making it easy to access the nut inside.