The Japanese spice sansho and the herb kinome come from the same plant, Zanthoxylum piperitum. Sansho, though, is derived from the seed pods of the plant, also known as Japanese prickly ash, while kinome refers to the leaves.
Both have a refreshing, zesty flavour and produce a tingling, tongue-numbing sensation that is reminiscent of Sichuan peppercorn - not surprising because they are from related plants.
Sansho powder is made by grinding the unripe seed husks - the hard seed inside is discarded. The fine pale green powder is used to balance the richness of fatty foods; it's a traditional accompaniment to grilled eel and is also served with some noodle dishes. Fresh, young seed pods are used whole to season pickles. The flowers of the plant are also edible, although, because the season is so brief, these are hard to find.
Kinome is often used as a palate-refreshing garnish on chawanmushi (steamed egg custard) and various types of fish, meat and vegetable dishes. A sushi chef taught me how to release the leaf's scent by placing it in one cupped hand then smacking it with the other cupped hand.