Wrap each cone tightly in the non-stick aluminum foil, covering it completely and tucking any excess foil into the cone cavity. Set aside.
Make an egg wash by beating the egg with 2 tablespoons of water. Set aside.
Flour the worktop roll out the pastry to 12 x 18 inches.
Trim the edges to neaten, then slice along the length into 15 equal strips of about 1 x 15 inches. Then cut 3 of the strips in half.
Starting with the pointy end, wrap the longer strips around the cones overlapping each twist of pastry by about a third as you go. If you have extra at the top, snip it off; don’t tuck it into the cone or it will be difficult to get the pastry off after baking.
Using the smaller strips, twist them gently and wrap the top of each pastry cone with the twisted strips. Trim any excess.
Brush them sparingly with the egg wash and then sprinkle with the sugar.
Lay the pastry cones on the baking sheet (placing any messy ends facing down, and chill for about 15 minutes.
Preheat the oven to 400°F/200°C
Bake for 20–25 minutes, or until a golden brown and puffy.
Remove from the oven and gently remove them from the molds/cones– remembering to hold the hot cones with a clean oven cloth. Cool completely.
For the Chocolate:
Make the chocolate by melting the butter and syrup together in a small saucepan. Once melted, remove from heat, add the chocolate and mix until fluid. Set aside to cool.
Spread one tablespoon of the chocolate into each horn
For the cream:
Add powdered sugar (to taste), skimmed milk powder (if using - This is to help give the whipped cream structure so it doesn't flatten out too quickly), and vanilla to the cream.
Using a food processor, whip the cream until it thickens enough to hold its shape (this doesn't take long at all so check often).
Pipe the cream into the horns and decorate with the remaining chocolate.
If you use the skimmed milk powder in the cream the horns will last up to 3 days.
If you don't use the powder, the cream should be made and the horns should be filled just before serving.