Crush cookies fine (There should be about 3 cups.).
Tip to speed the job: Place cookies, half at a time, in a plastic bag and crush with a rolling pin.
Place crumbs in a medium-size bowl; stir in half of the brown sugar.
Place apples in an electric-blender container cover.
Beat until smooth; pour into a medium size bowl; stir in remaining brown sugar.
Press about one third of the crumb mixture over bottom of a greased baking pan, 8x8x2 top with half of the apple mixture.
Repeat with another layer each of crumb and apple mixtures; sprinkle remaining crumb mixture over top.
Dot with butter or margarine; sprinkle lightly with cinnamon sugar.
Bake in a moderate oven (350°) for 30 minutes, or until firm and golden.
Cool slightly in pan on a wire rack.
Cut cake into 6 serving size pieces; top with whipped cream or your favorite custard sauce, if you wish.