2 ounces semisweet or bittersweet chocolate, melted
Cut a thin slice from the base end of the pears so that they will stand upright. Peel the pears.
In a nonreactive saucepan just large enough to hold the pears, combine the wine and sugar and cook over low heat until the sugar dissolves. Stand the pears upright in the pan and add the lemon zest, star anise and enough water to just cover the fruit. Simmer over moderate heat, partially covered, until the pears are tender when pierced with a knife, about 30 minutes.
Transfer the pears to a plate. Boil the poaching liquid over moderately high heat until reduced to 1/2 cup, about 30 minutes. Strain the syrup.
Using a melon baller, scoop out the core from the underside of each pear. Fill the cavities with the mascarpone. Stand the pears on 6 plates and spoon the syrup over them. Drizzle the melted chocolate on the plates and serve.
The pears and their syrup can be refrigerated for up to 1 day. Let return to room temperature before proceeding.