Mix flours with salt in medium bowl. Cut in Becel® sticks with finger tips or two knives until large crumbs begin to form; set aside. Blend water, yogurt and vinegar with wire whisk. While stirring flour mixture with a fork, gradually add just enough water mixture to form dough. Shape into a ball, then wrap in plastic wrap. Flatten dough into a disc and chill at least 30 minutes.
Blend pumpkin, evaporated milk, egg, egg whites, sugar, vanilla, spices and salt in medium bowl with wire whisk; set aside.
Set oven rack on bottom shelf of oven. Preheat oven to 400°F (200°C). Roll dough between large pieces of plastic wrap forming 30cm circle.Discard top piece of plastic, then turn dough into pie plate. If dough is a little sticky, brush with flour. Trim dough, then fold overhanging dough so it meets the edge of the pie plate and crimp edges.
Pour in filling, smoothing surface. Bake 15 minutes. Decrease oven temperature to 350°F (180°C) and continue baking 20 minutes or until center of pie is just set when wiggled. Cool completely on wire rack.