To assemble the rolls, cut 6 sheets of rice paper in half. Fill a large bowl with warm water and dip 1 whole sheet of rice paper in the water until it softens then lay flat on a plate. Dip a half sheet of rice paper in the water and lay it vertically in the middle of the round sheet. This will strengthen the roll, preventing the filling from breaking through.
In the middle of the rice paper, place 3 pieces of prawn in a horizontal line approximately 1 1/2-inches from the top. Below the prawns add some perilla leaves, pork, lettuce, mint, and vermicelli.
To form the roll, first fold the sides into the center over the filling, then fold the bottom of the rice paper up and over. Roll from bottom to top to form a tight roll, and just before you complete the roll add 2 pieces of garlic chives so that they stick out at one end.
Serve 2 rolls per person with dipping fish sauce.
Dipping Fish Sauce:
To make the dipping fish sauce: Combine the fish sauce, vinegar, sugar, and water in a saucepan and place on medium heat. Stir well and cook until just before boiling point is reached, then allow to cool. To serve, finely chop the garlic and chile and stir through with the lime juice.