01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - Roll out puff pastry on a lightly floured surface and cut into 12 equal rectangles. Arrange on prepared baking sheet, sprinkle with granulated sugar, then place a second sheet of parchment and another baking tray on top to prevent excessive rising.
03 - Bake for 15 to 20 minutes until crisp and deep golden. Transfer to a wire rack and cool completely.
04 - Whisk ricotta in a mixing bowl until completely smooth. Add powdered sugar, lemon zest, lemon juice, and vanilla extract, blending thoroughly.
05 - In a separate bowl, whip heavy cream to stiff peaks. Gently fold whipped cream into the ricotta mixture until uniform. Refrigerate until ready to assemble.
06 - Spread or pipe lemon ricotta cream onto six pastry rectangles, then place a second rectangle on top of each to form six napoleons.
07 - Dust the top layer of each mille feuille generously with powdered sugar and finish with a touch of fresh lemon zest. Serve immediately.