[Szechwan Peppercorns, Flower Pepper, Prickly Ash (English); Teppal (India); Jiao (China) Zanthoxylum piperitum, Z. simulans and others (citrus family)]
Dried fruits of the Chinese prickly ash tree. These "peppercorns" are essential to the famous Sichuan cuisine of China and a similar fruit is important in Nepal. The empty seed pods are used, the seeds themselves having been discarded. These pods are quite unique with a remarkably sharp, citrusy flavor and a numbing anesthetic effect on the tongue. Other countries have related species with flavors that vary more or less from the Chinese. Some of these are listed below.
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Sichuan Peppercorns were banned in the U.S. from 1968 to 2005 as a possible carrier of citrus canker but real enforcement didn't start until 2002 - then supplies started to dry up. They are now legally available again and in good supply. Current regulations require heating the peppercorns to 160°F/70°C after which they will be somewhat less red in color. There has been debate about how much this affects the flavor, but Sichuan recipes generally call for them to be toasted before use anyway, so this debate seems irrelevant.
The empty fruit shells are much used in Sichuan China and in the Himalayan region (Nepal, Tibet, Bhutan). In Japan the leaves (kinomie) are also used as a flavoring for soups and vegetables. The leaves are said to have a flavor somewhere between lime and mint. In general the fruits are dry roasted and then ground before adding to the recipe, usually near the end of cooking.
Subst: There is no real substitute, but if you can't get them use this formula: Grind together 1/2 t black peppercorns and 2 t coriander seeds. Add grated zest of 2/3 lemon (yellow only). This will fill in for about an equal measure of whole sichuan peppercorns. While it lacks the important numbing effect it will fill in for the flavor.
Varieties of this seasoning: