Pre heat your oven to 180c. Cut the prosciutto in half lengthways, and wrap one piece of prosciutto around an asparagus spear, leaving the tip exposed. Cut the pastry into 4, lay the asparagus and prosciutto across the 1/4 pastry on the diagonol, then pull it up to form an open ended parcel. Lightly brush with the beaten egg. Repeat with the remaining 15. Arrange on a baking tray and cook for 15 minutes or until puffed and golden. Serve with a sweet chilli sauce on the side.