Most Westerners aren't familiar with the numbing sensation that Sichuan peppercorns produce, so we don't have a word for it that people can easily understand. As Bradley suggested, "spicy and numbing" would be the shortest translation for an item on a restaurant menu, but otherwise it would be better to provide more detail. For example, you could say "flavored with chilies and Sichuan peppercorn" or "it combines the heat of chilies with the numbing sensation of Sichuan peppercorn" or something like that.