Preheat the oven to 200C, Gas Mark 6. Remove the packaging from the duck and place on a rack over a roasting tin. Roast for 1 hour or according to packet instructions until the skin is crisp and the duck is completely heated through. Remove from the oven and let rest for 20 minutes.
Carve the meat from the duck and cut into bite-sized pieces discarding the bones and any excessively fatty pieces of skin. Place in a large bowl with the lettuce, mango, spring onions, cashew nuts and coriander.
To make the dressing, place the Donegal Rapeseed Oil in a small bowl with the vinegar and hoisin sauce. Whisk until blended, then stir in the sugar, ginger and garlic. Season to taste.
Use the dressing to lightly dress the duck salad, tossing gently until evenly combined. Arrange on plates and serve the remaining dressing in a small jug so that your guests cal help themselves.