Place quince pieces and vanilla in a large pan and cover with water.
Boil for 30-40 minutes until the fruit is very soft.
Drain the fruit and weigh it to determine the required weight of caster sugar.
Blend the quinces in a food processor until very smooth.
Return the puree to the pan and add an equal weight of sugar.
Stir over low heat until the sugar dissolves.
Simmer for 1-1.5 hours until thick and deep orange in color.
Preheat the oven to 50°C.
Pour paste into a greased and lined 20cm baking tray and smooth the surface.
Dry in the oven for one hour to set.
Remove from the oven and slice into portions.