01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - Roll out the puff pastry on a lightly floured surface and cut into 12 equal rectangles. Arrange the rectangles on the prepared baking sheet, sprinkle evenly with granulated sugar, then place a second sheet of parchment on top followed by another baking tray to weigh them down and prevent excessive puffing.
03 - Bake for 15 to 20 minutes until the pastry is crisp and golden brown. Transfer to a wire rack and cool completely.
04 - In a mixing bowl, whisk the ricotta until completely smooth. Add the powdered sugar, lemon zest, lemon juice, and vanilla extract, then mix thoroughly until well combined.
05 - In a separate chilled bowl, whip the heavy cream to stiff peaks. Gently fold the whipped cream into the ricotta mixture in two additions until uniformly incorporated. Refrigerate until ready to assemble.
06 - Spread or pipe a generous layer of lemon ricotta cream onto six of the pastry rectangles. Place a second pastry rectangle on top of each to form six two-layer mille feuille.
07 - Dust the top layer of each mille feuille generously with powdered sugar and finish with a scatter of fresh lemon zest. Serve immediately.