12 tablespoons cold butter cut into tablespoon pieces
6 tablespoons chilled shortening cut into tablespoon pieces
10 to 12 tablespoons cold water
1 egg, lightly beaten
1/2 cup grated Gruyere or Swiss cheese
In a food processor combine the flour with the salt. Process the butter and shortening until they are cut into tiny pieces. Add 8 tablespoons of the water and process until it comes into a ball. If it is dry, add water by tablespoonfuls.
Turn the dough onto a board and press it into a round slab about 1-inch thick. If it is not too hot, roll the dough out immediately. (easier to handle) But if the fat is oozing out, then refrigerate for 2 hours at least or overnight to relax the dough.
Gently flour your board and rolling pin. Roll dough out from the center until it forms a circle about 1/2-inch thick; turn over and roll until a little thicker than 1/8th-inch thick and 14-inches in diameter.
Roll the dough over a lightly buttered 12inch false bottomed tart shell. Press the dough into the pan and trim the edges pressing up a border 1/2-inch wide. Fold that border back into the pan (it should not overlap the bottom) and press it back into the sides of the tart shell so that you are building up a double thickness of shell wall. Roll the rolling pin over the top to trim off excess pastry and refrigerate for 30 minutes.
Preheat oven to 400 degrees. Set the pan on a baking sheet. Line the dough with foil or parchment and fill it with dried beans. Bake for 10 minutes. Remove beans and bake 10 minutes longer. Paint the bottom of the shell with egg and sprinkle on grated cheese and return to oven for 3 to 4 minutes to really seal the bottom. Remove from oven and cool tart shell on a rack for 30 minutes before filling and finishing baking.