Making the pastry horns:
Step 1
Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
Step 2
Sprinkle some sugar on a clean surface and on top of the puff pastry sheet. Roll out the pastry into a rectangle approximately 9 by 12 inches.
Step 3
Cut the pastry into 12 strips, each about 1 inch thick.
Step 4
Wrap each strip around a horn mold, making sure the pastry overlaps by approximately half its length. Place the pastry-wrapped molds seam-side down on the prepared baking sheet.
Step 5
In a small bowl, beat the egg with one tablespoon of water to make the egg wash. Lightly brush each pastry cone with the egg wash, being careful not to let it touch the mold.
Step 6
Bake the pastry horns in the preheated oven for 15-20 minutes or until they are golden brown.
Step 7
Allow the baked pastry horns to cool for a couple of minutes before gently removing them from the molds. If any pastry sticks to the mold, gently press the mold to release it.
Step 8
Once the pastry horns are completely cooled, fill them with the chilled custard cream using a piping bag.
Step 9
Optionally, sprinkle the filled horns with powdered sugar before serving. Enjoy!