Step 1: Prepare the Puff Pastry

1. Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.
2. Lightly flour a clean surface and roll out the puff pastry sheet to ensure it’s even. Cut the sheet into 12 long strips, each about 1 inch wide.
3. Lightly grease metal cone molds or cannoli molds to prevent sticking. Starting at the pointed end, wrap each puff pastry strip around the mold, overlapping slightly as you go. Ensure there are no gaps.
4. Brush the wrapped pastry lightly with the beaten egg wash and sprinkle sugar evenly over each one. This will give the cannoncini a beautiful golden color and a slight crunch.

Step 2: Bake the Shells

1. Arrange the pastry-wrapped molds on the prepared baking sheet, leaving enough space between each to allow for puffing.
2. Bake for 15–20 minutes, or until the shells are golden brown and puffed.
3. Remove from the oven and allow the shells to cool slightly before carefully removing them from the molds. Be gentle to avoid breaking the delicate pastry.

Step 3: Make the Pastry Cream

1. In a medium saucepan, heat the milk over medium heat until it just begins to simmer. Do not let it boil.
2. In a separate bowl, whisk together the egg yolks, sugar, and cornstarch until smooth and pale.
3. Gradually pour the hot milk into the egg mixture while whisking constantly to temper the eggs and prevent curdling.
4. Return the mixture to the saucepan and cook over medium heat, whisking continuously, until it thickens to a pudding-like consistency. This should take about 5–7 minutes.
5. Remove from heat and stir in the vanilla extract and butter until fully incorporated. Transfer the pastry cream to a bowl, cover with plastic wrap (pressing the wrap directly onto the surface to prevent a skin from forming), and let it cool completely.

Step 4: Assemble the Cannoncini

1. Once the shells and pastry cream are completely cool, transfer the cream to a piping bag fitted with a round or star tip.
2. Carefully pipe the cream into each shell, filling from both ends to ensure they’re completely filled.
3. Dust the filled cannoncini with powdered sugar and drizzle with melted chocolate if desired.