Add the flour and salt (sugar if using) to the food processor, pulse to combine.

Scatter the butter cubes in the flour, and toss them a bit to coat them in flour so they don't stick together. 

Pulse the mixture in the food processor about 15 seconds until dough looks like course bread crumbs. 

Turn the food processor on and add the ice cold water 1 tablespoon at a time through the feed tube on the top. 

Pour the mixture out onto a clean surface and push the dough together and work it into a ball. Cut in two and shape dough into flat discs about the size and thickness of hockey pucks. 

Wrap in plastic wrap and refrigerate for at least an hour before rolling out. You can refrigerate it for up to 2 days or freeze it at this point. Proceed to "Rolling Out the Dough Section" if using the crust right away.

Combine the flour and salt (plus sugar if using) in a large bowl. Add the cold butter and using a fork or pastry cutter combine until you get a coarse mealy texture like bread crumbs. 

Add 4 tbsp of water and work into the dough, then add more as needed until you can bring the dough together and knead for just a minute or two till it comes together. 

Cut into two pieces and shape dough into flat discs about the size and thickness of hockey pucks. 

Wrap each piece of dough in foil and refrigerate at least an hour before rolling out. You can refrigerate it for up to 2 days or freeze it at this point. Proceed to "Rolling Out the Dough" section if using immediately.

Rolling Out the Dough 

Remove the dough discs and roll each out to the thickness of a pound coin or quarter with a rolling pin on a lightly floured surface. You will want to roll it out so you can cover over the edge of the pie pan.

Roll the dough into the pie pan and gently press into the dish. 

Trim the excess pastry around the edge, leaving ½ inch past the edge of the dish, using a knife or scissors. 

Crimp the dough by pinching it very firmly every ½ inch all the way around. 

Take a fork and prick the crust all the way around (this will help prevent air bubbles from forming)

Fill one crust and top with the other or roll both out and bake as directed.