Cook the rice according to the package instructions, mixing in the seaweed a few minutes before the end of cooking time. Cover and keep warm until time to serve.
While the rice is cooking prepare the tofu and vegetables: dice the tofu and marinate in soy sauce. Prepare the vegetables: wash and trim the broccoli and divide into florets. Blanch in boiling, salted water for 1-2 minutes, then drain, refresh in cold water and drain well. Clean the mushrooms and cut into bite-sized pieces.
Place the diced tofu on aluminium foil, preheat the grill and grill the diced tofu on the second shelf down for 10-12 minutes. Meanwhile peel and finely chop the onion and garlic. Heat the oil in a wok and fry the chopped onion and garlic. Add the mushrooms and broccoli and stir-fry, then add the chilli and stir-fry briefly.
Add the five-spice powder, soy sauce and oyster sauce. Finally stir in the vegetable stock and boil until reduced slightly. Serve the seaweed rice onto warmed plates, add vegetables and tofu and serve.