Heat the oil in a large lidded pan. Add the vegetables (including garlic, if using) and cook, stirring occasionally for 5 minutes.
Add all the other ingredients, bring to the boil and simmer gently with the lid on until thickened and the vegetables are tender. This will take 20-35 minutes, depending on the size of your vegetables. Add more water if too thick.
Serve in bowls, with your favourite breadsticks or use it to fill a jacket potato.