Preheat the oven to 330°F / 165°C.
Add the vinegar, brown sugar and vegetable stock and bring to a light simmer. Cover with the lid, transfer to the oven and cook for 2 hours. For the last 30 minutes of the cooking time, add the olives, cranberries, and chickpeas.
The leftovers also taste fabulous as the flavors have more time to meld.