01 - Preheat oven to 400°F. Line a rimmed baking sheet with parchment paper.
02 - Roll out the puff pastry on a lightly floured work surface. Cut into 12 even rectangles and arrange them on the prepared baking sheet. Sprinkle evenly with granulated sugar. Place a second sheet of parchment over the pastry and set another baking sheet on top to weigh it down and prevent excessive rising.
03 - Bake for 15 to 20 minutes until the pastry is deeply golden and crisp. Transfer to a wire rack and cool completely.
04 - In a medium mixing bowl, whisk the ricotta until completely smooth. Add the powdered sugar, lemon zest, lemon juice, and vanilla extract, then stir until evenly 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 no streaks remain. Cover and 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, gently pressing to level.
07 - Dust the top layer of each mille feuille generously with powdered sugar and garnish with additional lemon zest. Serve immediately.