In a small saucepan, whisk together apple juice and cornstarch until dissolved. Stir in blueberries, vanilla and cinnamon. Bring to a simmer over medium-high heat; simmer 4 to 6 min., or until blueberry sauce is slightly thickened. Let cool to room temperature; refrigerate until needed.
Place 2 small scoops of ice cream in each of 8 chilled decorative glasses or bowls. Spoon some of the blueberry sauce over top of each sundae; sprinkle with some of the almonds. Garnish each sundae with 1 mint sprig and serve.
To toast the almonds, place them in a single layer on a baking sheet. Bake in 325ºF (160ºC) oven for 10 to 12 min., or until lightly toasted.