First of all, in a large saucepan, bring your stock to the boil and then leave to simmer on a low heat.
In a separate saucepan, melt your butter over a medium heat and add the onion.
Fry your onion gently for a couple of minutes until it starts to sweat.
Now add your garlic and continue to cook for 2 more minutes.
Once the onion has started to soften, add your rice to the pan along with a pinch of salt and stir to coat the grains in the onion and butter mix.
Now add your mushrooms, mix with the rice and gently stir for a minute.
Take a ladleful of stock, add it to the mushrooms and rice and stir gently with a wooden spoon until the liquid has almost evaporated.
Now take another ladleful of stock and repeat the process, stirring gently until the liquid evaporates.
Continue to add stock, one ladleful at a time, and stirring until it almost evaporates.
Keep doing a taste test and when your rice is al dente and you have an oozy sauce, your risotto is cooked.
Remove the risotto from the heat, add a knob of butter and your parmesan cheese and stir into the rice.
Now add your spinach leaves, place a lid on the pan and leave to stand for 5 minutes.
After 5 minutes, remove the lid, stir in the wilted spinach and serve.
If you like, add a drizzle of olive oil and sprinkle with chilli flakes before eating.