Decide if you're making a savory or sweet pie and how many crusts you'll need. In a bowl, place the two cups of flour (and sugar if you are making a dessert pie, and salt, if you are not using salted butter). Measure the sour cream. Cut the butter into cubes and place into the flour / flour mixture.
Cover the butter cubes.
Use your fingers to smash the individual butter cubes into the flour mixture.
Work the two together so that the butter is into bits. It does not need to be fully uniform, but the butter pats should be small now.
Add the sour cream.
Use a metal fork or a pastry cutter to evenly combine.
Easily fold the dough together. This dough will be flexible and easy to handle.
Dust a little flour onto a clean, flat surface. If you are making a single batch - for one crust, form into one disk, wrap and refrigerate. If you are doubling this recipe for two crusts, form a ball, divide in two pieces, create two disks to wrap and refrigerate.
You can refrigerate the dough overnight. However, it's ready to work with in 15-30 minutes after being refrigerated. When you are ready, pre-heat your oven to 350 degrees. Dust a little flour onto a clean surface, and onto a rolling pin. Uncover the disk and roll out into an evenly-thin, round crust.
For a pie with a bottom crust: place the rolled dough onto a pie dish, cover bottom and form the edges in whatever pattern or design you'd like, and fill with the prepared fruit that that will be baked.
For a pie with a top pie crust, place the rolled out crust onto your prepared pie dish.
Cut off the edges with a pastry knife or food-scissors.
The dough is very pliable and easy to work with and manipulate, so you can decorate your pie however you wish. Here, I simply folded-in the edges for a chicken pot pie.
Anytime you have a top-crust, you must cut some little slits at the top so that it the pie can "breathe" while baking and bake properly.
My suggestion for all pie crusts, if you are not vegan or allergic to eggs, is to whisk a single egg white, and brush it over the top to totally cover the top crust. If this is a savory pie, leave it as is. It this is a sweet/dessert pie with a top crust, now is the opportunity to add sugar to the top before baking.
Now, it's time to bake. Place in the center of your oven at 350 degrees, for 30-50 minutes, depending on the coverage and how browned you'd like your crust. for a bottom-crust only pie, like this blueberry, you'll want to add sugar (if desired) after the pie is baked, and completely cooled.
Here's the end-result for a savory pie, with this crust at the top.