Cut duck into serving sized pieces and place in a glass or ceramic bowl.
In a food processor, blend chillies, garlic, vinegar, ginger, turmeric, cumin, coriander, cardamom, fenugreek and sugar. Blend until smooth. Pour the mixture over the duck and toss to coat. Cover and marinate 4 hours.
Remove the duck pieces from the mixture, reserving the mixture. Heat the ghee in a frying pan and add duck, cooking over medium heat 5 minutes or until browned.
Stir in the reserved mixture, reduce heat, cover and simmer 30 minutes or until tender. Add hot water from the kettle if needed to thin the gravy to your liking.