Put all of the meatball ingredients into a bowl, leaving out the olive oil. Mix together with your hands until well combined, then shape into 24 mini meatballs. Heat the oil in a large saucepan and brown the meatballs all over – you may have to do this in batches. Set the meatballs aside.
Cover the porcini mushrooms with 200ml hot water and leave to soak for 10 minutes. Meanwhile, add the onion to the pan and cook for 5-6 minutes until soft, before adding the garlic and cooking for another minute. Season well.
Add the chesnut and shiitake mushrooms and cook for 3-4 minutes until beginning to turn golden. Stir in the rice and cook for a minute until all the grains are coated in the mixture. Pour in the wine and turn the heat up for 2 minutes, until the wine has bubbled and reduced.
Drain and reserve the water from the porcini mushrooms. Over a medium heat, add a ladle of the porcini liquid, and allow to simmer gently for a few minutes until the rice has absorbed the liquid. Repeat, and when the porcini liquid is finished, continue this process with the stock for about 10 minutes. The rice will be plump and just tender.
Add the meatballs and an extra ladle of stock to the risotto. Allow to simmer for another 12-15 minutes, adding stock if it needs more liquid, until the meatballs are cooked through.
To serve, stir through the soaked porcini mushrooms, spinach and most of the parsley. Sprinkle with the parmesan shavings and reserved parsley to garnish.