Chao tong cai (炒通菜, stir-fried water spinach, also called morning glory or kong xin cai, 空心菜) with fermented tofu is one of the most popular and deceptively simple vegetable preparations in Cantonese cooking. The water spinach's hollow stems retain a pleasant snap while the leaves wilt quickly; the fermented bean curd (doufu ru) provides a rich, creamy, intensely savoury sauce that coats every leaf and stem without being heavy. It is a dish that tests wok temperature management — the water spinach must hit a screaming-hot wok to achieve the flash-wilt that preserves its texture.
The key: Maximum wok temperature. Water spinach is approximately 95% water by weight. When it hits the hot wok, it releases a flash of steam — if the wok is hot enough, this steam drives off quickly and the spinach wilts with bright colour and snap. If the wok is not hot enough, the steam steams the spinach in its own water, producing a limp, watery, discoloured result. The technique: Heat the wok until smoking. Add 2 tbsp oil. Add 2 cloves of garlic (sliced). Let the garlic sizzle 10 seconds. Add the water spinach (whole stalks, approximately 300g per person). Toss rapidly at maximum heat — the spinach will protest vigorously, releasing steam. After 60-90 seconds of rapid tossing, push the spinach to the sides of the wok. In the center, add 1-2 tbsp of red fermented bean curd (nan ru) or white fermented bean curd, mashed. Toss to coat every piece of spinach in the sauce. Season with a small amount of light soy and sesame oil. Total cooking time: 90 seconds to 2 minutes.
Fuchsia Dunlop, Land of Fish and Rice (2016); Fuchsia Dunlop, Every Grain of Rice (2012)