Preheat oven to 150°C (130°C fan-forced).
For the spiced quinces, peel, core & quarter the quinces. Tie the peelings & cores together in a piece of muslin.
Place the remaining ingredients together in a large ovenproof pot over a low heat, stirring until the sugar dissolves.
Increase heat to medium-high, bring to the boil & cook for 2 minutes.
Submerge the quince pieces & the muslin bag in the spiced syrup, adding extra water if required to cover quinces.
Place a dampened piece of baking paper directly over the top of the quinces, (called a cartouche) which helps slow down the evaporation of moisture.
Cover with a lid & place pot in preheated oven for 4 hours or until quinces have turned a deep ruby colour. Remove from heat & allow to cool.
Serve quinces on top of porridge, with Greek yoghurt & pistachios or add them to a frangipane tart for something special.