To make the crust: In a medium-sized mixing bowl, whisk together the flour, salt and sugar., Using a pastry blender, pastry fork, your fingers or a mixer, cut in the butter and shortening, leaving pea-sized crumbs., Sprinkle the crumbs with enough ice water to make them cohesive. Squeeze them into a ball, wrap with plastic wrap, and chill at least 1 hour., Preheat the oven to 400°F., Roll the pastry into a 12" circle, and place it in a 9" pie plate. Crimp the edges, and chill the crust while you're preparing the filling., To make the filling: In a medium-sized mixing bowl, whisk together the eggs, sugar, salt, maple syrup, melted butter and maple flavor., Stir in the nuts and pour the filling into the prepared crust., Bake the pie on the bottom rack of the preheated oven for 15 minutes. Lower the oven temperature to 350°F and bake for an additional 25 to 35 minutes, or until the center is set., Refrigerate for up to 5 days.