Add the pears and crushed cloves to a preserving pan. Pour over the wine and measurement water to just cover the base of the pan, then bring to the boil. Cover and cook gently for 30 minutes, stirring from time and breaking up the pears with a wooden spoon or potato masher, until very soft.
Allow to cool slightly, then purée in small batches in a food processor or liquidizer, or press through a sieve.
Weigh the purée, then pour back into the rinsed preserving pan. For every 500 g (1 lb) of purée add 375 g (12 oz) sugar. Heat gently, stirring from time to time, until the sugar has dissolved.
Cook over a medium heat for 45–60 minutes, stirring more frequently towards the end of cooking, until the mixture has darkened slightly and is so thick that the wooden spoon leaves a line across the base of the pan when drawn through the mixture. Skim with a draining spoon or stir in the butter if needed.
Ladle into warm, dry jars, filling to the very top. Clip on lids, label and leave to cool.
To serve, this makes a good accompaniment for cheese, crackers and grapes.