Roll 1 piecrust into a 12-inch circle on a floured surface. Fit into an 11-inch tart pan with removable bottom. Prick bottom and sides of pastry shell.
Bake at 375 for 5 minutes.
Let cool in pan on a wire rack.
Sprinkle with chopped hazelnuts.
Beat eggs at high speed of an electric mixer.
Add pumpkin and next 9 ingredients; beat well.
Pour into pastry.
Bake at 375 for 35 minutes. Cool in pan on wire rack. Cover and chill at least 2 hours.
Cut 30 shapes from remaining piecrust using a small leaf cookie cutter.
Place on an ungreased baking sheet.
Bake at 450 for 6 minutes.
Remove to a wire rack; let cool.
Beat whipping cream until foamy; gradually add powdered sugar, beating until soft peaks form. Fold in crystallized ginger. Cover and chill 1 hour.
Arrange whole hazelnuts and pastry leaves on tart.