1. Prepare the heart and liver if required.
2. Skin the onion and slice it thinly. Put it in a pan with a little water and simmer for 5-7 minutes until softened.
3. Drain, and chop it finely with the duck heart and liver.
4. Mix with the breadcrumbs and parsley.
5. Melt the butter and stir it into the mixture. Season to taste.