01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper and set aside.
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 a second baking tray to weigh them down and prevent excessive puffing.
03 - Bake for 15 to 20 minutes until the pastry is golden brown and crisp throughout. Transfer to a wire rack and let 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 stir 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, being careful not to deflate the cream. Refrigerate until ready to assemble.
06 - Spread or pipe a generous layer of the lemon ricotta cream onto six of the pastry rectangles, then place a second pastry rectangle on top of each to form six individual mille feuille.
07 - Dust the top layer of each assembled mille feuille with powdered sugar and finish with a touch of fresh lemon zest. Serve immediately for the best texture contrast.