Halve any larger chestnut mushrooms. Zest the lemon and set to one side. Squeeze the juice into a large bowl. Peel and grate the ginger. Finely chop the chilli, flicking out most of the seeds. Add the ginger and chilli to the lemon juice.
Add the tamari and 2 tsp caster sugar to the bowl. Pour in 1 tbsp olive oil. Whisk together well. Add the whole shiitake mushrooms and chestnut mushrooms to the bowl and mix well to coat in the marinade. Set to one side.
Peel and finely chop the onion and carrot. Heat a saucepan. When warm, drizzle in 1 tbsp olive oil. Add the onion and carrot. Cook for 5 mins till softened.
Rinse the rice under cold water and tip it into the pan with the softened veg. Add 2 tsp China 5 spice, the lemon zest and stir. Pour in 400ml boiling water. Add a pinch of salt. Cover, bring to the boil, then turn the heat down. Simmer for 25 mins till all the water is absorbed. Take off the heat. Set aside, lid on, to steam in the pan.
Finely shred the cavolo nero. Tumble the marinated mushrooms onto a foil lined grill pan or tray. When the rice has 10 mins left to cook, heat your grill to a medium high setting. Slide the tray under the grill for 5 mins.
Add the shredded cavolo nero to the rice while it's steaming and place the lid back on. Baste the mushroom skewers with any remaining marinade. Put under the grill for a further 5 mins.
The mushrooms should be cooked and the cavolo nero wilted. Heap the spiced veg rice onto a couple of place. Spoon over the yakitori mushrooms and any cooked marinade.