3/4 cup whole milk
2 egg yolks
1/4 cup granulated sugar
1 tablespoon flour
1 1/2 teaspoons vanilla extract
9 sheets frozen phyllo pastry (such as Athens), thawed
1/3 cup heavy cream
4 tablespoons unsalted butter, melted
2 tablespoons confectioners sugar
In small heavy-bottomed saucepan, bring 1/2 cup of the milk to a boil. In a small bowl, whisk remaining 1/4 cup milk, egg yolks and sugar until smooth. Whisk in flour. Whisk a little hot milk into egg yolk mixture. Stir egg yolk mixture back into saucepan. Cook over medium heat, stirring constantly, until thick, and mixture comes just to a boil, 3 minutes. Reduce heat to medium-low; cook 2 minutes, stirring constantly. Remove from heat. Stir in vanilla. Pour into small bowl, cover surface directly with wrap; cool to room temperature. Refrigerate until cold.
Meanwhile, heat oven to 375 F. Coat a 15 x 10 x 1-inch jelly roll pan with nonstick cooking spray. Spread one pastry sheet on prepared pan. Brush with butter. Repeat layering with all of the pastry sheets and butter. With sharp knife, cut sheets lengthwise into thirds. Cover with a sheet of nonstick foil and a second baking pan.
Bake at 375 F for 15 to 18 minutes or until pastry layers brown nicely. Remove top pan and foil; let cool.
In a small bowl, beat cream to stiff peaks. Stir custard; fold in cream. Place one pastry strip on cutting board. Spread half of the custard onto pastry. Top with second pastry strip, then gently spread with remaining custard. Top with final pastry strip; dust with sugar. Slice into pieces with a serrated knife. Serve within 2 hours of layering.