Bring the 2 cups of water to a boil and add the prawns,removing them as soon as they are cooked.Put them in a bowl of ice water to stop the cooking. When cooled, peel the prawns and leave aside for garnishing.
Blend garlic, shallots, preserved soy beans, dried prawns, dried chillies, candlenuts, lemongrass and shrimp paste into a paste.
Fry paste in 1/3 cup oil, till fragrant.Add tamarind juice and 1 cup of stock from cooking the prawns.Bring to a boil and simmer for five minutes.
Add noodles and stir-fry. Mix in tofu and toss well. Add sugar, pepper, fish sauce and a squeeze of lime juice.
Lastly add in the beansprouts and the chives toss until breansprouts and chives are just limp.