Measure the flour and sugar into a medium bowl. Cut in butter with a pastry blender until mixture is crumbly. Add sour cream and mix lightly with a fork until dough clings together and starts to leave sides of bowl.
Gather dough together with hands and knead a few times. Wrap dough in wax or parchment paper. Chill over night for best results. You can also use it after chilling a few hours, but overnight is best.
Roll pastry out in the shape you want and make your turnovers. I usually roll out in a rectangle and cut in strips (see picture above), put a filling on one side, fold over and press firmly with the end of a fork. Bake 25 minutes at 350.