Polish puff pastry cream cake (kremowka)

Instructions

1. Preheat oven to 200°C (400°F) with racks in upper and lower third position and line two baking sheets with nonstick baking mats. Divide puff pastry into two equal pieces. Sprinkle work surface with granulated sugar and roll out each piece of pastry to a 23 cm x 33 cm (9 in x 13 in) rectangle. Transfer to prepared baking sheets and bake, rotating halfway, until puffed and deep golden brown, about 35 minutes. Cool completely on a wire rack.
2. Whisk together ¾ cup granulated sugar, cornflour and salt in a medium saucepan. Whisk together milk and egg yolks in a glass measuring cup. Add milk mixture to the saucepan, along with the 42g butter. Cook over medium heat until mixture comes to a boil. Let boil 1 minute. Remove pastry cream from heat.
3. Strain pastry cream through a fine-mesh sieve into a bowl. Cover with plastic wrap, pressing it directly onto the surface of the pastry cream to prevent a skin from forming. Refrigerate until chilled, at least 2 hours or up to 2 days.
4. Place remaining butter in the bowl of a stand mixer fitted with the paddle attachment. Beat on medium speed until smooth. Reduce speed to low and add vanilla bean seeds and cooled pastry cream, ½ cup at a time. Increase speed to medium-high and beat until light and fluffy, about 2 minutes.
5. Place one rectangle of puff pastry on a cutting board and spread with pastry cream mixture. Top with second puff pastry rectangle and press gently to adhere. Loosely cover and refrigerate to set, at least 1 hour or up to 8 hours. To serve, slice with a serrated knife into 7.5 cm (3 in) squares. Dust with icing (confectioners’) sugar.