Marinate the tempeh in a bowl with Teriyaki sauce overnight in the fridge, or as long as you can. If in a rush this step can be done just before cooking.
Firstly crack on with the rice. Add mushrooms to a large frying pan or wok. Dry fry for a couple of mins then add in the sesame oil (this helps the mushrooms not absorb all the oil) Cook for 5 mins then add in the spring onions, fry for a further 1 min. Next bung in the rice and miso, stir and cook till the rice is hot.
Start the tempeh while mushrooms are cooking. Get another pan on the heat, add in the oil and tempeh pieces (leaving the marinade behind) Fry till slightly caramelised then add in the marinade and cook till the tempeh is glazed.
Now for the bok choy. Add the sesame sauce and bok choy to a pan, stir fry for 2 mins then cover with a lid or baking tray to steam until the stems are just soft.
Pile rice into a bowl, top with boy choy, tempeh and sesame seeds.