In a bowl, stir together the flour, salt and sugar. Add the butter and shortening.
Cut the butter and shortening into the flour (I do this by rubbing with my fingers) until the mixture resembles coarse crumbs.
Add ice cold water, little by little, mixing as you go until the dough can be gathered into a ball. The dough should NOT be sticky.
Divide the dough into two portions, one slightly larger than the other.
Take the larger portion and roll between two large pieces of baking (wax) paper, starting at the center and rolling outward in all directions. Keep rolling until the dough is less than a quarter of an inch thick.
Remove the top layer of wax paper. Lift the dough by holding the edges of the bottom piece of wax paper and invert onto the pie dish. Peel off the wax paper and pat the dough to fit into the dish snugly.
Roll the remaining piece of dough but keep it covered with wax paper.
When the filling has been poured into the dough-lined pie pan, remove the top piece of wax paper from the prepared smaller crust. Hold the bottom piece by the edges to lift the crust and invert it over the filling. Trim the top crust so that the overhang is a bit longer than that of the bottom crust. The longer overhang of the top crust makes folding and sealing easier and it prevents the formation of a too thick crust along the edges.
Fold the overhang of both the top and bottom crusts, pressing them tucking underneath. Crimp the edges: Place your left thumb on the edge of the crust. Place the thumb and forefinger of your right hand on top of the crust to within half an inch of the left thumb (do the reverse if you’re left-handed). Push your left thumb inward while your right thumb and forefinger push outward. Keep doing this until the edges of the crust are uniformly crimped.
Take a thin knife and punch slits all over the top crust. You can also use a fork. This is not for decorative purposes but to create holes to let steam from the filling escape. Otherwise, the top crust will bubble up and create a space between it and the filling.
Next, beat and egg with a little milk. Brush the mixture all over the top crust including the edges.
Your pie is now ready to go into the oven.