Peel each pear; remove core from bottom end, leaving stem end intact. If needed, slice about 1/4 inch from base of each pear so that it will sit flat. Brush pears with orange juice.
Combine wine and cranberry-raspberry juice in a medium saucepan; bring to a boil. Place pears, stem end up, in pan. Cover, reduce heat, and simmer 15 minutes or just until pears are tender. Remove pears from liquid with a slotted spoon. Reserve poaching liquid for another use, if desired.
Combine powdered sugar, cocoa, and cornstarch in a small saucepan. Gradually add water, stirring until smooth. Cook, stirring constantly, over medium heat until slightly thickened. Remove from heat, and stir in vanilla.
Spoon 1 tablespoon chocolate sauce into each of 2 dessert dishes; place pears on sauce. Drizzle 1 tablespoon chocolate sauce over each pear. Garnish with orange zest, if desired.