Boil the chestnuts separately, if using dried soak overnight. Put the brown lentils in a pan, cover with cold water and bring to the boil. Simmer uncovered until soft. In a hot skillet, sear the ducks on both sides until golden and finish cooking in a preheated oven at 160C.

Meanwhile, bring the beef gravy to the boil and reduce. In another pan, fry the onion until soft, add the pineapple and sugar and cook until caramelized.

Add the vinegar and set aside. To serve, make a bed of lentils on a serving plate, cut the duck on the slant and place it on top.

Add the chestnuts to the gravy and pour on one side of the plate and on the opposite side of the plate put the pineapple relish. Serve immediately.