1.In a medium bowl, combine chopped vermicelli with wombok, mint, sugar and juice; season to taste.
2.Shell and devein prawns; chop meat finely.
3.Meanwhile, make hoisin dipping sauce.
4.Dip one rice paper round into bowl of warm water until soft; place on board covered with tea towel. Top with a little of the prawn meat and noodle filling. Fold and roll to enclose filling. Repeat with remaining rounds, prawn meat and noodle filling.
5.In a small bowl, combine hoisin sauce with rice vinegar to make dipping sauce. Serve rolls with hoisin dipping sauce.