Peel and core pears; cut in half lengthwise, and brush with 2 teaspoons lemon juice.
Combine wine and next 3 ingredients in a large saucepan; bring to a boil. Add pears; cover, reduce heat, and simmer 15 minutes or until tender, turning once. Transfer pears and poaching liquid to a bowl; cover and chill thoroughly.
Drizzle half of melted chocolate evenly onto 6 dessert plates. Transfer pears to plates, using a slotted spoon. Discard poaching liquid. Top each pear with 1/4 cup sherbet. Drizzle remaining chocolate evenly over sherbet. If desired, garnish with fresh raspberries and mint sprigs. Serve immediately.