In a medium mixing bowl, whisk the flour, sugar and salt to combine.
Add the butter to the flour mixture and toss to coat.
Put the bowl in the freezer for 10 minutes.
Turn the mixture onto a clean, dry counter (marble is best) and roll over it with a rolling pin to flatten the butter pieces. Using your hands or a bench scraper, gather the mixture together and then roll over it again with a rolling pin.
Repeat one more time, then scrape the mixture back into the bowl and place in the freezer again for 5 minutes.
Turn the mixture back onto the counter and roll and scrape it together three more times. Place it in the freezer for another 10 minutes, then remove the bowl from the freezer and gently fold in the sour cream. Shape the dough into a ball. If the dough isn't moist enough to hold its shape, add 1-2 T of cold milk.
Cover the dough with plastic wrap and refrigerate for at least 30 minutes, then divide the dough in half and roll out to fit your pie plate.
When crust is shapened, proceed by pre-baking or filling ~ according to your recipe.