One hour before mixing, cube the butter and measure the shortening. Chill both of them in the refrigerator. 

Prepare a reserve of ice water in a small bowl. You will measure your water from this bowl.

In a medium bowl, combine the flour and salt.

Add the cubed butter. Gently flatten each cube with fingers. Coat them in the flour mixture. Add the chilled shortening and mix with a pastry blender. Blend until the mixture becomes a coarse, pea sized crumb texture.

Slowly add the ice water 2 Tablespoons at a time to the flour mixture, folding with a rubber spatula. Continue to add just enough water until dough is almost entirely hydrated. It should be in several larger size crumbs, with a bit of loose flour in the bottom of the bowl. You may not need to use all of the water. 

Turn the mixture out onto a work surface and pinch the dough together with your hands, gathering any loose bits of flour and pressing it into the dough. Gently fold or knead dough a few times, just enough to get it to form a cohesive ball of dough. If the dough isn't coming together and is too dry, wet your hands with the ice water and work it into the dough to hydrate it a bit more. A well-mixed pie dough should show pieces of butter and shortening throughout, be soft without being too sticky, and should be pliable and cohesive. 

Divide dough into two equal pieces. Round and flatten into a disc shape. Wrap each with plastic wrap and chill for at least two hours before rolling out.

When rolling out, flour surface and roll out slightly, rolling from the center outwards. Turn dough a quarter turn and roll out a little bit more. Continue turning and rolling until dough is rolled out into a 12 inch circle. 

Place in pie dish and trim off any extra dough around the edges with scissors, leaving about a 1/4-inch overhang for shaping the edges. For easy dough transfer, roll up the dough onto a rolling pin and unroll it over the pie dish. Crimp edges as desired. 

Brush the edges with an egg wash. 

Bake as directed for your pie recipe.