1. Fry the onions in a large deep pan in a bit of butter.
2. Tip in the rice and heat for a few minutes.
3. Pour in the stock and boiling water, allow it to boil, then turn right down. Put the lid on and leave to simmer for about 10 minutes.
4. Add the veg into the pan with the parsley and the rest of the butter, stick the lid back on, and leave to simmer for another 10.
5. Carefully stir everything up and add a generous splash of rice vinegar to serve.