Preheat oven to 190ºC . Combine crust ingredients in bowl and mix well. Set aside quarter cup for topping. Pat remaining mixture into 23 cm round pie pan or oven proof dish. Bake 10 minutes. Cool. Mix together all filling ingredients (ice cream should be softened) with fork or large spoon. Turn into cooled pie shell; smooth top with knife. Sprinkle reserved crumbs mixture on top. Freeze till firm, at least 2 hours. Remove from freezer about 15 minutes before serving. Less filling than pumpkin pie