For a garlic-chive omelet, omit the water chestnuts and scallions and add 9 ounces of garlic chives, washed and cut into quarter-inch pieces.
Use a knife to peel dark skin off fresh water chestnuts. If using canned water chestnuts, rinse and drain. Slice into thin rounds.
Place water chestnuts in a bowl. Add eggs and salt. Mix well with a fork, 1 to 2 minutes.
Place a wok on its stand over high heat for 1 minute. Add oil; swirl to coat sides of wok. Heat for 2 minutes. Add egg mixture. Gently move eggs in wok with a spatula, lifting sections of eggs onto sides of wok, until puffed slightly and lightly browned, 2 to 6 minutes. Turn out onto a plate. Top with scallions, cut into wedges, and serve.