Meanwhile, prepare the plum sauce by cutting and dicing the plums into small cubes (remove the pits first), then add them in a medium-sized saute pan with the granulated sugar.
Break the cinnamon into small pieces then mince the onions into fine pieces, then add them to the mix.
Squeeze in a zesty orange juice and water, then turn up the pan to medium heat and bring it to a boil.
Season the sauce with salt and pepper to taste but don’t forget that you’re salting the duck breasts too. You can taste the mix every now and then to see if it has reached the desired level of seasoning.
If the cinnamon or ginger feels too strong at any point, simply take them out. Once the mixture starts boiling, lower the heat and leave the sauce to simmer for about 10 to 15 minutes or until the sauce reduces to a fairly thick puree, then set aside to cool.