1.Place dried chillies in small heatproof jug, cover with boiling water; stand chillies 15 minutes, drain.
2.Meanwhile, shell and devein prawns, leaving tails intact.
3.Blend or process soaked chillies, galangal, lemon grass, coriander root and stem mixture, garlic, paste, half the oil and half the lime leaves until mixture forms a paste.
4.Transfer paste mixture to large bowl, add prawns; mix well.
5.Heat remaining oil in wok; stir-fry prawn mixture with remaining lime leaves until prawns are changed in colour. Add the water, sauce and sugar; stir-fry 1 minute. Remove from heat; toss apple, shallot, coriander leaves and fresh chilli into stir-fry.
When purchasing coriander, make sure you buy stems that also have the root attached for this recipe. Wash the coriander under cold water, removing any dirt clinging to the roots; scrape the roots with a small flat knife to remove some of the outer fibrous skin. Chop coriander roots and stems together to obtain the amount specified.