Take the duck breasts and trim off the excess fat and sinew.  Score the fat on the duck breast in a criss-cross fashion and place to one side.  

Pre-heat a frying pan with the sunflower oil and butter and place the duck breasts fat side down and cook until golden brown.   Then turn over the duck breasts and seal.  Place the duck breasts, covered, in the fridge.

Take the oranges and zest three of them and juice all six.  Place the brown sugar into a pan on a medium heat and stir with a wooden spoon until melted.  Add the orange juice and stock and once brought to the boil turn down the heat and reduce by half.  Then add the orange zest. 

Pre-heat your oven to 200°C and place the duck breasts on a baking tray fat side up.  Cook the duck breasts for 10 minutes for pink meat and longer if you prefer your duck more well done. 

Once cooked remove the duck breasts from the oven and leave to rest for  a minute or two.  Then slice the duck breasts and arrange onto plates and pour over the sauce.