In blender or food processor, blend vanilla wafer cookies and walnuts into fine crumbs. Transfer to 9 inch pie pan. Mix in butter and maple syrup. Using a fork, press firmly and evenly onto bottom and sides of pie pan to create a crust. Chill 10 minutes in freezer.
In large bowl, blend vanilla ice cream, pumpkin and pumpkin pie spice. Spoon into pie crust. Smooth top with a spatula. Chill 1 hour in freezer, or until firm.
Before serving pie, place heavy cream and granulated sugar in small bowl. Mix with an electric mixer on high speed until peaks form. Spoon into pastry bag with a star tip and pipe around edge of pie.
In small saucepan over low heat, melt shortening and chocolate chips, stirring occasionally, until smooth. Transfer to small plastic container and chill in freezer 30 minutes, or until firm.
Remove chocolate from container. Using vegetable peeler or cheese slicer, scrape chocolate to form small curls. Use curls to decorate pie.