Blueberry Lemon Filling:

1. In a saucepan, combine fresh blueberries, granulated sugar, lemon zest, lemon juice, and cornstarch.
2. Cook over medium heat, stirring frequently, until the mixture thickens and the blueberries release their juices. This usually takes about 5-7 minutes.
3. Remove from heat and let the blueberry lemon filling cool to room temperature.

Pastry Layers:

1. Preheat your oven to 400°F (200°C). Roll out the puff pastry sheets on a lightly floured surface.
2. Cut the pastry into desired shapes or squares, and place them on a baking sheet lined with parchment paper.
3. Bake in the preheated oven for 10-12 minutes or until the pastry is golden brown and puffed.
4. Allow the pastry layers to cool completely before assembling.

Whipped Cream:

1. In a bowl, whip the heavy whipping cream until soft peaks begin to form.
2. Gradually add powdered sugar and vanilla extract, continuing to whip until stiff peaks are achieved.

Assembling the Napoleon:

1. Place a pastry layer on a serving plate.
2. Spoon a portion of the blueberry lemon filling onto the pastry layer, spreading it evenly.
3. Add a layer of whipped cream over the blueberry filling.
4. Repeat the layers, finishing with a dusting of powdered sugar on top.
5. Chill the Blueberry Lemon Napoleon in the refrigerator for at least 1 hour before serving.
6. Slice and serve this delightful dessert, savoring the combination of flaky puff pastry, sweet blueberry lemon filling, and light whipped cream.