First prepare the tofu. Cut into 1 cm thick slices. Line a plate with a few pieces of kitchen paper and place the tofu slices on top. Cover with a few more pieces of kitchen paper, another plate and place something heavy (a couple of cans will do) on top. Leave to press whilst you prepare the other ingredients, at least 10 minutes or so. You may need to change the paper halfway through.
Cook the black rice. Rinse and place in a small saucepan with a pinch of salt and a cup (250 ml) of cold water. Bring to the boil, stir once and place a lid on the pan. Turn the heat down low and cook for about 25 minutes, until tender. You can rinse it once cooked, but I like it when it's a bit sticky.
Once the tofu is dry, cut into 1 cm dice. Sprinkle with the cornflour, 5-spice powder, chilli powder and a good pinch of salt and toss well. Heat the oil in a wok or large frying pan. Add the tofu (I did this is two batches) and fry until golden brown and crispy - this took 2-3 minutes for me. Transfer to some more kitchen paper to drain.
Stir fry the mushrooms, broccoli and pak choi, adding more oil if needed. Place in a bowl along with some rice and crispy tofu pieces.
Place all ingredients for the sauce in your empty wok or frying pan and bring to the boil. Cook for a minute until slightly thickened and pour over the rice, veggies and tofu. Garnish with the spring onions, coriander and sesame seeds, if liked and serve.