01 -
Heat the milk in a saucepan until just below boiling. In a separate bowl, vigorously whisk egg yolks, granulated sugar, vanilla extract, and flour until the mixture is pale and creamy. Gradually stream the heated milk into the egg mixture while whisking continuously. Return the mixture to the saucepan and cook over medium heat, stirring constantly, until the custard thickens to a creamy consistency. Remove from heat, transfer to a bowl, cover, and refrigerate for 1 hour to chill.
02 -
Preheat oven to 200°C. Roll the puff pastry on a surface dusted with granulated sugar into a 23 x 30 cm rectangle. Slice into 12 strips. Tightly wrap each strip around a horn mold, overlapping edges. Arrange on a parchment-lined baking sheet with seam side down. Beat the egg with 1 tablespoon of water, then brush mixture lightly over each pastry. Bake for 15–20 minutes until golden brown. Allow pastry horns to cool slightly before removing from molds.
03 -
Transfer chilled custard cream to a piping bag. Pipe cream into each cooled pastry shell. Dust with powdered sugar before serving.