Heat a medium saucepan over medium heat, add the oil and fry the onion, garlic, carrot, celery, potato and zucchini. Fry for about 6 minutes until softened, then add the tomato, oregano and bay leaf and stir through.
Add the stock and salt and bring to a simmer. Simmer covered for 10 minutes. Taste and adjust seasoning, then serve as a side dish with a little drizzle of olive oil on top.
