Grate chilled butter. Allow to set for a few minutes - just enough to take the chill off, but don't let it get soft.
In large bowl, whisk together with a whisk or fork, flour, salt, and sugar.
Incorporate butter into flour mixture using pastry blender or knife and fork until it resembles coarse meal.
Add sour cream and using the pastry blender or a fork, work it into the flour and butter mixture.
Usig your hands, work the dough into a ball. Split into two discs. Cover with airtight covering and refrigerate at least an hour, up to 24 hours.
Remove from refrigerator. Let it sit out for a few minutes so it's not warm, but it's pliable. Roll each disc (if needing two, or freeze the other) out on a flat, lightly floured surface until you have a circle 10-14" in diameter. Lift a portion of it up every now and then to be sure it's not sticking. If it is, add a little more flour to your surface area. You'll want it to have an even thickness.
Add one rolled out crust to pie plate.