Grate the zest of 2 organic oranges & put the mess in a pot.
Squeeze the oranges & add the juice (150 ml - only!).
Add the orange liqueur & the sugar & bring to a boil. Whisk until the sugar is dissolved completely.
Add the duck stock & bring again to a boil.
Add the concentrated stuff & whisk until dissolved.
Add salt & pepper to taste.
Mix cold water & starch & add gradually to the boiling mess. Whisk again until dissolved & the sauce has satisfyingly thickened.