Basic pie pastry:
(Makes enough for a double-crust 9-inch pie)
In a large bowl combine the flour, sugar and salt. Using the largest holes on a box grater, grate the shortening and butter into the flour mixture. Sift the mixture through your fingers until it is crumbly. Stir in the cold water, adding just enough so the pastry comes together in a ball. Divide the dough into two disks, wrap with plastic and chill until ready to use.

Pie Filling:
Preheat oven to 425 F. Line a 9-inch pie plate with pastry. Brush the bottom unfilled pastry with a beaten egg and refrigerate for 5 minutes. Remove from refrigerator, cover with foil, weigh down with rice or pie weights and bake for about 7-10 minutes. In a medium bowl, stir together the grapes, sugar, cornstarch, cinnamon and salt. Pour into the pastry. Sprinkle with the lemon juice and dot with the butter. Top with the remaining pastry and press to seal. Flute the edges and cut vents into the top of the pie. Bake in preheated oven for 10 minutes, then reduce the heat to 350 F and cook 30 to 35 minutes more, or until the filling in the center is bubbly.