In a large bowl, add the flour, salt, sugar and whisk together.
Grate the butter over the bowl, and gently mix together with the flour. Make sure all the butter has been coated with flour.
Add the sour cream and mix until dough comes together. It should feel sticky but not unmanageable.
Divide the dough into two sections and pat down into a round. You can go ahead and roll out the bottom crust now and add it to the pie pan. Refrigerate while the filling is being made.
Notes
This recipe makes enough for 2 pie crusts. If you only need a single pie crust, use 1.5 cups flour, 2 tsp sugar, 1/4 tsp salt, 1/2 cup butter (1 stick), and 1/2 cup full fat sour cream.