Cut butter into flour until mixture resembles coarse crumbs OR put flour and cold butter, which has been cut into 1/2" cubes, in a food processor and mix using pulse until mixture resembles corn meal. Put butter-flour mixture in a large bowl. Stir in the sour cream until dough just holds together.Turn dough onto lightly floured surface and with lightly floured hands, knead gently 2 or 3 times. Flatten into disc shape.

To make a single crust; on a lightly floured surface, roll out 1/2 the dough to 11" to 12"circle. Fit into 9"pie plate; trim, leaving 1"overhang.Dampen underside of overhang with water, turn under; flute edges or make decorative edging. Place in freezer 10 min..NOTE : Unused dough can be frozen,wrapped tightly, in foil or wrap for 2 months.

To make a double crust;Roll out dough as for single crust; fit into pie plate, trim. Roll out rest of dough to a 12" circle.

Fit over top of filled pie,trim, leaving 1" overhang. Dampen edge of pastry with water; press together or turn under, flute or decorate edge. With tip of sharp knife, cut vents in center of top crust.