Bring 2 1/4 cups of water to a boil in a large, tightly covered saucepan. Stir in the rice and quickly replace the lid. Reduce the heat to low and cook for 10 minutes. Remove from heat and let stand, still covered for 5 minutes.
Meanwhile, cut the bok choy in half to separate the leaves from the stems. Cut the leaves into wide shreds and finely slice the stems.
Heat the oil in a wok and add the onion. Stir-fry over medium-high heat for 2 minutes, until just tender. Add the pepper and bok choy and stir-fry for 3 minutes.
Add the mushrooms, garlic, ginger, and chili, and stir-fry for 3 minutes, until the mushrooms are just soft. Drizzle with soy sauce and toss to combine. Serve immediately with the rice. Serves 4.