If not already done, clean and gut fish. Chop the head and tail off and reserve. Split the fish body at the spine and chop the body into 1” wide chunks.
In your wok, boil several cups of water (enough to cover the mung bean sprouts). When water boils, put the mung bean sprouts in and blanch for about 1 minute Drain and put blanched sprouts in a large dry bowl. Dry wok.
Pour oil in wok and heat on medium-to-high flame. When oil is hot, add the Sichuan peppercorns and chilis. When they smoke and fill air with their fragrance (it may make you cough, so put on the vent fan), add the ginger and the garlic. Toss ingredients in the oil for a moment, and then add the fish chunks (including the head and tail). Continue tossing until the outside of the fish chunks are seared. Add enough water to barely cover the fish, put a lid on and stir and simmer until the fish is done (flesh is cooked through and meat comes easily off the bones). Salt to taste.
Remove fish chunks and place on top of mung bean sprouts, then pour wok liquid over fish. Top with cilantro.
Note: Serve with plenty of rice to soak up all the spices.