To make rolls: Bring a medium stockpot of lightly salted water to the boil. Add pork, reduce heat and simmer for about 10 minutes until cooked through and no longer pink in the middle. Allow pork to cool, then slice into thin strips.
Bring another stockpot of lightly salted water to the boil. Cook prawns 2 to 3 minutes, or until opaque. Drain, allow to cool slightly and pat dry with paper towels. Peel, devein and slice in half.
Again, bring a stockpot of water to the boil and cook vermicelli until tender, stirring occasionally, about 7 to 8 minutes. Strain, and rinse well to prevent sticking.
Fill a medium bowl with warm water. Dip each rice paper wrapper in water for about 30 seconds until soft and flexible. Place wrapper on a flat surface, and put 2 basil leaves in the centre, side by side, about 5cm from edge of wrapper. Place 4 to 5 prawns halves on the basil, followed by a small amount of pork, then a small amount of noodles. Sprinkle with coriander, mint, and top with beansprouts. Starting at one end, roll the wrapper over once, fold both sides in towards centre, and continue rolling as tightly as possible without tearing. The result should be a roll about 3 or 4cm thick. Serve rolls with hoisin-peanut sauce for dipping.
To make sauce: Warm hoisin sauce, peanut butter and water in a saucepan over medium high heat. Bring to the boil, then immediately remove from heat. Pour sauce into a serving bowl and garnish with chopped peanuts.