Mille-Feuille (Napoleon)

Instructions

1. Preheat oven to 400°F (200°C). Line two baking sheets with parchment paper.
2. Roll out the cold puff pastry on a lightly floured surface to a 1/8 inch (3 mm) thickness. Trim edges to form a neat rectangle approximately 12 x 9 inches (30 x 23 cm).
3. Cut the rolled dough into 10 equal rectangles (about 3 x 4.5 inches each). Prick all rectangles all over with a fork to prevent over-rising.
4. Place pastries on prepared sheets. Mix the egg and water to make an egg wash, and brush lightly over the pastry surfaces.
5. Bake for 12-15 minutes until golden and puffed, then turn off the oven and leave pastries inside for 5 minutes for extra crispness. Remove and cool completely on wire racks.
6. For the vanilla pastry cream, split the vanilla bean and scrape seeds. Combine the whole milk with the seeds and pod in a saucepan and heat until just simmering. Remove from heat and let infuse for 15 minutes. Remove the pod.
7. In a bowl, whisk together egg yolks, granulated sugar, and cornstarch until pale and smooth. Gradually whisk the hot milk mixture into the egg mixture.
8. Return mixture to saucepan and cook over medium heat, whisking constantly until it thickens and reaches 175°F (79°C). Remove from heat and stir in unsalted butter until melted. Cover surface with plastic wrap and chill for at least 1 hour.
9. To assemble, spread a layer of pastry cream on one puff pastry rectangle, then top with another pastry layer. Repeat to create stacks of two layers each (or three for a taller mille-feuille).
10. Prepare icing by mixing the confectioners' sugar with milk and a pinch of salt until smooth and pourable but thick enough to coat a spoon.
11. Spread or pipe icing on the top layer of each mille-feuille. Optionally pipe thin lines of vanilla bean paste or melted dark chocolate on the icing and drag a toothpick through to create a marbled pattern.
12. Chill the assembled pastries for 15 minutes to set the icing before serving. Dust lightly with extra powdered sugar if desired.