Measure out, cut, and group together each section’s ingredients: In a bowl, toss the lamb with its seasonings, including the cornstarch and wine, so it is thoroughly coated. Have the ginger and garlic ready to go into the wok, and have the onion, water chestnuts, and snow peas piled on a piece of paper towel, ready to go. In a small bowl, blend the sauce ingredients together. With this lineup, the stir-fry will easily come together in a few minutes.
Set a 14- to 16-inch wok or a straight-sided 12-inch sauté pan over high heat. When it is hot, swirl in 1 1/2 tablespoons of the vegetable oil. Add the lamb and stir-fry for 90 seconds. Spread the lamb out as you cook it, so all its sides sear. Immediately remove the lamb to a clean bowl. Wipe out the wok with a thick wad of paper towels.
Heat the wok again over high heat. Swirl in the remaining 1 1/2 tablespoons oil. Sir in the ginger and the garlic, and stir until fragrant (few seconds), sprinkling with the salt. Immediately add the vegetables. Stir-fry for 1 1/2 to 2 minutes. Add the sauce mixture, and continue stir-frying for another 90 seconds.
Turn the lamb into the wok, and stir-fry for about 10 seconds to heat it through. Stir in the cashews, and turn the mixture into a serving bowl. Serve immediately.