In food processor with knife blade attached or in blender at high speed, blend gingersnaps and 2 tablespoons sugar until fine crumbs form.
Preheat oven to 375 degrees F. In 9-inch pie plate, with fork, stir crumbs with melted margarine or butter until moistened. With hand, press mixture onto bottom and up side of pie plate, making a small rim. Bake crust 8 minutes. Cool crust on wire rack.
Meanwhile, in 2-quart saucepan, mix cornstarch with 2 tablespoons cold water until blended. Add half the blueberries and 1/2 cup sugar to cornstarch mixture; heat to boiling over medium-high heat, pressing blueberries against side of saucepan with back of spoon. Boil 1 minute, stirring constantly. Remove saucepan from heat; stir in remaining blueberries.
Pour blueberry mixture into crust. Cover with plastic wrap and refrigerate until well chilled, about 5 hours. Serve with whipped cream if you like.
