01 - Preheat the oven to 400°F. Line a baking tray 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 tray, 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 deeply golden. Transfer to a wire rack and let cool completely.
04 - In a mixing bowl, whisk the ricotta until smooth and creamy. Add the powdered sugar, lemon zest, lemon juice, and vanilla extract, then mix thoroughly until well combined.
05 - In a separate 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 it. Refrigerate until ready to assemble.
06 - Spread or pipe a generous layer of lemon ricotta cream onto six of the pastry rectangles. Top each with a second pastry rectangle, pressing down gently.
07 - Dust the top layer of each mille feuille generously with powdered sugar and garnish with fresh lemon zest. Serve immediately to maintain the pastry's crisp texture.