Begin by cutting lamb leg into 2/3" cubes for even cooking. In a mixing bowl, combine the lamb with soy sauce, Shaoxing wine, and salt. Stir well to ensure the lamb is evenly coated with the mixture. Allow it to marinate for at least 20 minutes.

While the lamb marinates, mix together the cumin powder, Sichuan chili flakes, sugar, and optional Sichuan peppercorns in a small bowl. Set it aside to infuse its flavors.

Drain any excess liquid from the lamb cubes and sprinkle cornstarch over the lamb, tossing gently to coat each piece.

Heat a large skillet over high heat and add 3 tablespoons of peanut oil. Once hot, carefully add the marinated lamb in a single layer, searing each cube for about 1-2 minutes per side until golden brown. Transfer cooked lamb to a plate.

In the same skillet, add more oil if needed, then toss in the dried Chinese chili peppers, diced onion, minced ginger, and garlic. Cook for about 2-3 minutes or until onions soften and become fragrant.

Return the seared lamb to the skillet with the cooked aromatics, sprinkle the prepared spice mix over the top, and stir well to coat every piece thoroughly. Cook for another 1-2 minutes.

Gently toss in fresh cilantro as a final burst of flavor, stirring for just another minute. Your Real-Deal Xinjiang Cumin Lamb is ready to serve. Enjoy!