Dainty Sichuan calls this dish "spicy lamb kebabs" on its menu. Tina Li says they roast and grind the cumin and Sichuan pepper for their distinctive scent and taste. She adds a small quantity of water to the marinade and binds it with potato flour - this helps the lamb stay juicy. Begin this recipe a day ahead to marinate the lamb, although at a pinch 20 minutes will do the trick.
Note Potato flour is available from select health food shops and supermarkets, and Asian grocers. Along with the requisite Sichuan pepper, Dainty Sichuan uses Maggi Seasoning (as soy sauce), Knorr chilli liquid seasoning, and shisanxiang, or 13-fragrance spice powder. The latter is used in Chinese-Islamic cooking, especially for marinating kebabs. They're all available from Chinese grocers.