In a heavy saucepan combine the sugar, the rum, and 1/2 cup water and simmer the mixture for 2 minutes. Add the pear, peeled, halved, and cored, and the apricots and poach the fruit, covered, spooning the syrup over the pear occasionally, for 8 to 10 minutes, or until the pear is tender. In a small heavy saucepan combine the chocolate, 2 tablespoons water, and the vanilla and heat the mixture over low heat, stirring constantly, until it is smooth. Transfer the pear halves to a work surface, cut them diagonally, into 1/4-inch-thick slices, and fan them onto 2 plates. Sprinkle the apricots over the pear slices and spoon the chocolate sauce around the fruit.
