Peel the pears, leaving the stalks on; remove the 'eye' from underneafh and slice a little off so that the pears will sit upright.
Place the sugar, water, vanilla and cloves in a small saucepan and dissolve the sugar over low heat, then boil rapidly for 1 minute.
Place the pears upright in the syrup and poach them for 15-20 minutes, then lift them out with a perforated spoon and place on a serving dish.
Cool and chill thoroughly.
Just before serving, place the chocolate and water in a small bowl fitted over a pan of simmering water.
When the chocolate has melted, add the butter and cream and beat till smooth.
Pour the sauce over the pears and serve at once.
Fan-shaped wafers or langue du chat biscuits [cookies] make a nice accompaniment.