Notes: Lemongrass, 2 stalks pounded then cut crosswise into finger lengths, 3 inches. Szechwan Peppercorns should be just the blossoms, not the seeds, available in Asian markets.
Combine all the ingredients except for the lemon zest in a heavy, non-aluminum 1 1/2 quart saucepan. Bring to 223 F degrees on a deep fry thermometer over moderately low heat and let bubble for 15 minutes.
Remove the pan from the heat and let stand for 5 minutes, then stir in the lemon zest and let stand overnight or until cool.
Remove and discard the lemongrass. Scrape the oil and seasonings into an impeccably clean container.Use immediately - do not store for any length of time!