Arrange the lime and ginger on a sheet of baking paper. Place the pork on top. Roll up in baking paper. Place in a bamboo steamer over a wok of simmering water. Cover and Steam for 20 minutes or until pork is cooked through. Allow to cool then thinly slice.
For the dipping sauce; Combine all the ingredients in a saucepan over medium heat. Cook, stirring, for 3–4 minutes or until warmed through, adding more water if necessary (the sauce should resemble the consistency of thick cream). Set aside.
Cook the noodles following packet directions. Drain and refresh in cold water then drain again. Slice the prawns in half lengthways.
Half-fill a shallow dish with warm water. Dip 1 rice paper wrapper in the water and remove straight away (it should still be firm). Place on the workbench. Stand for 20–30 seconds or until soft enough to roll without splitting. Place 2 prawn halves at 1 edge of rice paper. Top with pork, noodles, mint, beansprouts and mushrooms. Roll up wrapper, folding edges in to enclose filling. Cover with a clean tea towel. Repeat with the remaining ingredients. Serve with warm or room temperature dipping sauce.