Rhubarb Sour Cream Pie

In bowl, mix flour with salt. Using pastry blender or 2 knives, cut in butter and shortening until mixture is in fine crumbs with a few larger pieces. In liquid measure, beat egg yolk with lemon juice; mix in enough ice water to make 1/3 cup (75 mL). Drizzle over dry ingredients, stirring briskly with fork to form ragged dough. Press into disc. Wrap in plastic wrap and refrigerate for at least 30 minutes or until chilled. (Make-ahead: Refrigerate for up to 3 days.)

 On lightly floured surface, roll out pastry to 1/8-inch (3 mm) thickness; fit into 9-inch (23 cm) pie plate. Trim edge to leave 3/4-inch (2 cm) overhang; fold overhang under and flute edge.

Filling: Arrange rhubarb evenly in pie shell. In bowl, whisk together egg, sugar, sour cream and flour until smooth. Pour over fruit.

Topping: In small bowl, mix flour with sugar. Drizzle in butter and mix with fork until crumbly. Sprinkle over filling.

Bake in bottom third of 450°F (230°C) oven for 15 minutes. Reduce heat to 350°F (180°C); bake until edge is puffed, filling is slightly jiggly and topping is golden, about 40 minutes. Let cool completely on rack before cutting.