Peel and core pears; cut in half lengthwise, and brush with lemon juice.
Cut vanilla bean in half lengthwise. Scrape seeds into a large saucepan. Add vanilla bean halves, 1 cup maple syrup, and apple juice to saucepan; bring to a boil. Add pears; cover, reduce heat, and simmer 15 minutes or until tender, turning once. Remove and discard vanilla bean halves. Transfer pears and poaching liquid to a bowl; cover and chill thoroughly.
Combine sugar and water in a small saucepan; bring to a boil, stirring frequently until sugar dissolves. Add whipping cream; bring to a boil. Remove from heat. Add margarine and chocolates; stir until chocolates melt. Stir in remaining 1 tablespoon maple syrup. Cool completely.
Transfer pears to 6 dessert plates, using a slotted spoon. Discard poaching liquid. Top each pear with 1/2 cup ice cream. Spoon chocolate sauce evenly over ice cream, and sprinkle evenly with almonds. Serve immediately.