1. Prick the duck and season well.
2. Put the pieces on a wire rack in a roasting pan so that the fat runs off the duck.
3. Roast at 220°C (425°F) Gas 7 for 10 minutes then reduce the heat to 180°C (350°F) Gas 4 for a further hour.
4. Mix the cornflour with a little pineapple juice.
5. When the duck is cooked, remove the pieces from the pan and place each one on a piece of pineapple on a clean dish.
6. Keep them warm while you make the sauce.
7. Remove as much fat as possible from the pan, leaving the juices.
8. Mix the cornflour mixture into the juices over a gentle heat, cooking this for 2 minutes.
9. Add the rest of the pineapple juice and warm the sauce through.
10. Add the sour cream and stir it through.
11. Spoon the sauce over the duck.
12. Sprinkle the paprika over the top and either serve it immediately or keep it warm in a low oven for up to 15 minutes.