Place the chicken in a large heavy-based saucepan, and add the tamarind, ginger, chopped chiles, onion, lemongrass and garlic. Finely slice the coriander stalks and add to the pan, keeping the leaves until later.
Cover with water to the top and weight the chicken down with a heavy lid or a smaller pan that fits inside the cooking pan. Bring to the boil and slowly simmer for 1 hour to 1 hour and 30 minutes. Once cooked, remove the chicken and pull off the meat using a fork.
Mash up the sauce and add the coconut milk and a lug of fish sauce. Put the rice noodles in a bowl, pour over boiling water and leave to stand for 3 minutes. Mix the coriander leaves with the finely sliced chile.
Drain the noodles, place some in the bottom of each serving bowl, and dress with soy sauce to season. Pile the chicken on top, then pour over the strained sauce. Pile the chile and coriander mix on top and drizzle with olive oil.
* Found in Asian markets.