Rose Napoleons

Whisk egg yolks and sugar in a medium bowl until pale and frothy. Sift flour and cornstarch into egg mixture; whisk to combine. Put milk into a small pot and bring to a simmer over medium-high heat. Pour milk into egg mixture in a slow, steady stream while whisking vigorously. Transfer egg–milk mixture to the pot and cook over medium-low heat, whisking constantly, to make a thick custard, 5–6 minutes. Remove from heat and stir in rose water and vanilla. Transfer mixture to a bowl; let cool over an ice bath. Cover surface with plastic wrap; refrigerate until ready to use.

Preheat oven to 350°. Put 1 sheet of phyllo on a parchment paper–lined baking sheet, brush with some of the butter, and top with a second sheet of phyllo. Butter top, then repeat process to make 6 layers in all. Repeat process on a second baking sheet with remaining phyllo and butter. Top each stack with a sheet of parchment paper, followed by a baking sheet to weight them down. Bake until light golden brown, 25–30 minutes. Let cool completely (with baking sheets on top). Using a sharp knife, cut each stack into thirty 2" × 2" squares. Reserve phyllo scraps.

To assemble: Place 1 phyllo square on a platter, dollop with a generous teaspoon pastry cream, and top with a phyllo square. Continue building layers until you have 5 layers of phyllo and 4 layers of pastry cream in all. Repeat with remaining phyllo and pastry cream to make 12 napoleons in all. Dust napoleons with confectioners' sugar, sprinkle with pistachios, and crumble some of the reserved phyllo scraps over the top. Serve immediately.