Combine brown sugar, granulated sugar and cornstarch in small saucepan until blended. Stir in cranberries, currants, cinnamon and allspice. Bring to simmering over medium heat, stirring. Cook 5 minutes or until thickened and cranberries are tender. Remove from heat. Stir in walnuts and lemon juice. Cool completely.
Cut puff pastry sheet in half. Roll out each half into 15 x 7-inch rectangle; square off sides. Place 1 rectangle on ungreased baking sheet; refrigerate.
Assembly and Topping:
Cut three 1-inch-wide lengthwise strips from remaining sheet; reserve scraps. With egg, brush 1-inch border around edge of rectangle on baking sheet, being careful not to get egg on edge of pastry; this will keep the pastry from rising properly.
Attach 2 strips down length of tart. Cut two 5-inch strips for ends from third strip; attach. Prick center of tart all over with fork. Freeze 10 minutes. If desired, cut pear shapes from pastry scraps for garnish.
Heat oven to 400 degrees F. Lightly brush tops of attached pieces with egg, without getting egg on edges; score lightly with knife if desired.
Bake tart in 400 degree F oven for 15 minutes or until pastry is golden brown. Bake cutouts for about 8 minutes or until golden brown. Remove to wire rack to cool.
Up to 3 hours before serving, spoon cranberry mixture in tart shell; spread level. Arrange pear slices on top; brush with Jelly Glaze. Garnish with mint and whipped cream, and pastry cutouts if desired. Makes 10 servings.
Heat 1/4 cup apple jelly and 2 teaspoons orange-flavored liqueur in saucepan until smooth.