Preheat the oven to Gas Mark 6, 200°C, fan 180°C.
In a large pan, heat 2tbsp 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 the remaining olive oil, Parmesan and some seasoning.
Spread the mixture over the beans and bake for 30 minutes, until bubbling and crisp.