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. Cut into 12 equal rectangles. Place on the prepared tray, sprinkle with granulated sugar, and cover with another sheet of parchment paper and a second baking tray to prevent excessive puffing during baking.
03 - Bake for 15 to 20 minutes until crisp and golden brown. Remove the top tray and parchment for the final 5 minutes if additional browning is needed. Cool completely on a wire rack.
04 - In a mixing bowl, whisk the ricotta until smooth and creamy. Add the powdered sugar, lemon zest, lemon juice, and vanilla extract. 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 until fully incorporated and no streaks remain. Refrigerate until ready to assemble.
06 - Spread or pipe an even layer of lemon ricotta cream onto six of the pastry rectangles. Top each with a second pastry rectangle, pressing gently to adhere.
07 - Dust the top layer of each mille feuille generously with powdered sugar. Garnish with additional lemon zest if desired. Serve immediately for the best texture contrast.