Preheat the oven to gas 6, 200C, fan 180°C In a large pan, heat 2 tbsp olive oil. Fry the onions and garlic with some salt and a grind of black pepper for 10 minutes or until soft. Add the tomatoes, drained beans, vinegar, basil and stock, and pour into a baking dish. In a bowl, mix the breadcrumbs with remaining olive oil, Parmesan and some seasoning. Spread the mixture over the beans and bake for 30 minutes, until bubbling and crisp.