Heat the oven to 220C/200C fan/gas 7. Heat 1 tbsp of the oil in a shallow ovenproof casserole over a medium heat and gently fry the sausages for 5-8 mins, or until brown on all sides. Transfer to a plate using tongs. Tip the onions into the pan and fry for 5-8 mins until beginning to turn golden. Drizzle in a little more oil if the onions start to stick. Sprinkle in the sugar and cook for a minute before stirring in the vinegar, tomato purée and paprika to form a paste. Tip in the tomatoes, then pour the wine into the tomato can, swish it round, and add to the pan. Stir in the bay leaves and beans, then arrange the sausages on top so they’re half-submerged in the sauce but still a little exposed.
Bring the mixture to a simmer, then bake in the oven for 20 mins. Meanwhile, make the topping. Mix the breadcrumbs with the garlic and parsley, then season and stir in 1 tbsp oil. Scatter the topping over the casserole, then drizzle with the remaining 1 tbsp oil and bake for 10 mins more until the breadcrumbs are golden and crisp. Leave to stand for a few minutes, then take to the table and serve from the dish.