In a saucepan, combine cranberries, sugar, cinnamon sticks, ground cloves, freshly grated nutmeg, mango juice and water.
Stir to combine.
Bring to a boil. Cook on medium high heat for 15 minutes, until the cranberries are soft.
With a potato masher, crush the cranberries.
Add the pinch of salt and stir to combine.
Remove the cinnamon sticks, if desired for a more refined sauce.
Return to the heat and cook another 5-10 minutes (add agar agar if using), until the sauce starts to pull away from the pan.
Leave to chill.