Gan bian (干煸, literally dry-fry or dry-stir-fry) is a Sichuan technique in which ingredients are cooked in a wok with very little oil over sustained medium-high heat until almost all their moisture is expelled, concentrating their flavour and creating a wrinkled, slightly chewy texture. The process is slow by Chinese wok standards — 5-8 minutes of continuous tossing — and requires patience. The resulting ingredient is then flavoured with Sichuan aromatics and spices. Gan bian si ji dou (干煸四季豆, dry-fried green beans) and gan bian niu rou si (干煸牛肉丝, dry-fried shredded beef) are the two most famous gan bian preparations.
The gan bian sequence: 1. Start with very dry ingredients — green beans washed and dried thoroughly, or beef shredded and squeezed of moisture. 2. Heat the wok with 1 tbsp oil (much less than a regular stir-fry) over medium heat. 3. Add the ingredient and toss continuously. The ingredient will sputter and release steam as moisture exits. 4. After 5-8 minutes, the ingredient becomes wrinkled, slightly blistered, and reduced in volume by 30-40%. It should be dry to the touch and lightly charred in spots. 5. Clear a space in the center of the wok, add aromatics (ya cai 芽菜 preserved mustard greens, dried chilli, Sichuan peppercorn, garlic) and briefly fry. 6. Toss everything together. Season with soy sauce and a few drops of chilli oil. For green beans specifically: The beans must have no visible water on them when they enter the wok — steam will cause them to stew rather than dry-fry. Some recipes call for deep-frying the beans first (guo you) then dry-frying — this accelerates the moisture removal.
Too much oil: Even a small excess of oil turns the dish into a regular stir-fry — the gan bian technique requires almost no oil after the initial coat. Too-high heat: High heat scorches the surface before the interior moisture is removed. The gan bian process is medium, sustained heat.
Fuchsia Dunlop, Land of Plenty (2001); Fuchsia Dunlop, The Food of Sichuan (2019)