Stir pear nectar, white wine and sugar in heavy large saucepan over medium-high heat until sugar dissolves and syrup comes to boil. Add pears to syrup in saucepan. Cover pan, reduce heat to medium-low and simmer until pears are tender, about 8 minutes. Using slotted spoon, transfer pears to plate. Increase heat to medium-high and boil poaching liquid until reduced to 3/4 cup, about 8 minutes. Remove pan from heat. Add chocolate; whisk until chocolate melts and sauce is smooth. Place 1 warm pear half, cut side up, on each plate. Top with vanilla ice cream and warm chocolate sauce. Or cover pears and chocolate sauce separately and refrigerate up to 2 days; then serve pears cold with ice cream and sauce, rewarming sauce, if desired.