Heat a wok or large skillet over high heat. Add 2 tablespoons of the oil and heat for 30 seconds. Add the pork and stir-fry until no trace of pink remains, 3 to 4 minutes. Transfer to a plate. Wipe out the pan. Reduce heat to medium-high, add the remaining oil, and heat for 30 seconds. Add the peppers and cook, stirring constantly, for 1 minute. Add the broccoli and water. Cover partially and cook, stirring occasionally, until almost tender, about 3 minutes. Add the Hot-and-Sour Sauce and increase heat to high. When it starts to bubble, add the water chestnuts and pork. Stir-fry until warmed through, about 1 minute. Add the nuts and toss again. Serve immediately over the rice.
Tip: You can use chicken or shrimp instead of the pork. Or try bok choy instead of broccoli.