Arrange pear halves, cut side up, in an ungreased 13" x 9" baking dish.
Stir together ginger ale and next 3 ingredients.
Pour ginger ale mixture over pears; sprinkle with 1/4 teaspoon cinnamon.
Cover and chill at least 3 hours or overnight.
Remove pears from refrigerator, and let stand at room temperature 30 minutes.
Uncover and bake at 350° for 40 minutes.
Melt jelly in a small saucepan over low heat; stir in remaining 1/4 teaspoon cinnamon and 3 tablespoons pan juices.
Remove pears from baking dish using a slotted spoon.
Place pears in a serving dish; pour jelly mixture over pears.
Serve with Mock Devonshire Cream.
Garnish, if desired.