Fluffy, lightened creme patissiere and the best berries go inside layers of puff pastry for this spectacular take on a traditional French dessert.
Prepare the Puff Pastry.
Preheat the oven to 375 degrees. Sprinkle work surface with sugar. Roll dough into a rectangle 1/8 inch thick and, using a sharp knife or a pastry cutter, cut in half. Cut each half into thirds, keeping rectangles equal sized, each approximately 6 inches by 8 inches. Water-spray two baking sheets and place pastry rectangles on them. Chill until firm, about 30 minutes.
Prick rectangles all over with fork tines. Place a wire rack over each set of pastry rectangles and bake until pastry reaches the top of the rack, about 15 to 20 minutes. Remove rack and continue to bake until golden and evenly browned, about 5 to 10 minutes more. Cool completely on racks.
Make pastry cream: Scald the milk, vanilla bean, and 1/4 cup sugar. Beat egg yolks with remaining sugar until thick. Sprinkle in flour and cornstarch, and continue beating until well mixed.
Remove vanilla bean from milk. Beat half of the hot milk into yolk mixture. Return this to remaining hot milk and bring to a boil quickly, whisking very fast to prevent scorching. Remove from heat and pour into a bowl to cool. Rub top of pastry cream with butter to prevent a skin from forming. Cover with plastic wrap and cool completely. Immediately before using, fold in softly whipped cream with a wooden spoon.
To assemble, slice each rectangle horizontally. Place each bottom half on a serving plate. Top with a 1/2-inch layer of pastry cream and berries. Place the top half on top of berries and repeat process with remaining rectangles. Sprinkle top layer with confectioners' sugar. Garnish with berries and serve immediately.
A black steel pan sprayed with water works best when baking sugary puff pastry dough.