Place flour, salt and butter in a food processor. Whirl until coarse crumbs form. Add sour cream and egg yolk. Whirl just until dough starts to form a ball. Or place flour, salt and butter in a bowl. Using a pastry blender or 2 knives, cut in butter until mixture resembles coarse crumbs. Stir in sour cream and egg yolk just until mixture starts to form a ball.
Form dough into a ball, then cut in half. Shape each into a disc, then wrap in plastic wrap. Refrigerate at least 1 hour or up to 3 days or freeze up to 1 month. Bring to room temperature before rolling. Great for our Apple-Cranberry Pie or use to make your favourite fall pies.
This no-fail pie dough is a favourite of the Chatelaine test kitchen.