unfold puff pastry and place each sheet on a baking sheet. bake according to package directions, until golden. allow pastry to cool.
meanwhile, in a large bowl, whisk pudding mix and milk until thickened. stir in half of the whipped topping until thoroughly mixed.
break cooled pastry into large pieces and place one third of them into bottom of trifle dish or large glass bowl. spoon half of the pudding mixture over that and drizzle with one third of the chocolate syrup.
repeat the layers then top the remaining pastry pieces, the remaining whipped topping and the remaining chocolate syrup.
cover and chill for at least 2 hours before serving.
notes: for really rich flavor and texture, whip 2 cups (1 pint) heavy cream and use that instead of the whipped topping.