Cut sheet on puff pastry into 3 long strips, along the folds of the puff pastry sheet. Prepare puff pastry according to package directions. Coll completely.

Cut each pastry strip in half with a knife. Then, divide each puff pastry piece in half by pulling apart the top and bottom into two layers. {Look at the photo. It will make more sense.}

In a medium bowl, stir together Cool Whip and preserves until smooth and well combined.

Place one layer of puff pastry on a plate. Top pastry with about 1/3 cup Cool Whip mixture. Top Cool Whip with 8 blackberries. Top with puff pastry, Cool Whip mixture, and 8 blackberries. Top napoleon with one more piece of puff pastry. Dust napoleon with powdered sugar.

Repeat with remaining pastry, Cool Whip, and berries. Serve immediately.