Place the onion, carrot, celery, potato and chopped tomatoes in a large heavy-based stockpot over medium heat. Pour in the water and bring to the boil. Reduce heat to low and simmer for 1 hour.
Take the stockpot off the heat. Transfer the carrots and potato to a chopping board and finely chop. Strain the vegetable soup through a fine sieve into a clean saucepan, using the back of the ladle to extract as much flavour as possible. Season the soup with salt to taste.
Place the saucepan with strained brodo vegetale back onto medium heat. Bring to the boil. Add the risoni pasta, referring to the cooking time specified in pasta packet instructions.
To serve, divide the chopped carrots and potato among serving bowls. Ladle hot brodo vegetale over the carrots and potato. Top with Parmigiano Reggiano– buon appetito.
2 tablespoons (40ml) extra virgin olive oil|1 onion, whole|1 large carrot, roughly chopped|1 stalk celery, roughly chopped|1 potato, whole|200g Italian chopped tomatoes|2 litres water|200g risoni pasta|Sea salt, freshly ground black pepper