Heat the oven to 190°C (375°F) Gas 5.

Prick the duck pieces all over with a fork, season with salt and pepper and place on a rack in a roasting tin. Roast for 1 1/4 hours, until the duck pieces are cooked through (the juices run clear when the meat is pierced with a fine skewer). Remove the duck pieces from the tin, drain on absorbent paper and place in a large casserole. Turn the oven down to 180°C (350°F) Gas 4.

Drain off all but 1 tablespoon fat from the tin and transfer the tin to the top of the cooker. Add the onion and garlic, if using, and fry gently for 2 minutes.

Gradually stir in the stock and sherry and bring to the boil, stirring constantly. Stir in the baked beans in their sauce, the tomato ketchup, garlic sausage, thyme and bay leaf. Season to taste with salt and freshly ground black pepper.

Pour the mixture over the duck pieces in the casserole. Cover and cook the casserole in the oven for about 30 minutes.

Increase the oven heat to 220C/ 425F/Gas 7. Mix the parsley and breadcrumbs together and sprinkle evenly over the surface of the casserole. Return to the oven and cook for a further 15 minutes, uncovered, to brown the topping. Serve hot.