1. In a large pot, bring the water to a boil with the sugar, orange slices, cinnamon stick, bay leaf and clove; stir to dissolve the sugar. Add the pears and prunes and cook over moderate heat, turning the pears often, until the pears are tender, about 25 minutes.
2. Using a slotted spoon, transfer the pears and prunes to a shallow serving bowl. Boil the poaching liquid over high heat until reduced to 1 1/2 cups, about 10 minutes. Strain the syrup over the pears. Serve warm or at room temperature, with the butter cookies alongside.