Combine lemongrass, chile peppers, galangal, ginger, shrimp paste, shallots, garlic and peanut oil to a blender or food processor. Pulse until well combined. Blend in the cilantro, turmeric, sugar and tamarind and pulse until it has made a paste. Reserve until ready to use. Make paste one day ahead of time for flavors to blend.
Directions for broth and assembling soup:
1. Heat oil in a large pot over medium heat. Stir spice paste into oil and heat for a few minutes. Add chicken stock and let it come to a boil. Lower heat to low and add in cilantro, basil and fish sauce and let gently simmer.
2. Meanwhile, cook the noodles in boiling water until tender. When ready to serve, stir the coconut milk into the hot broth. Place noodles in a large bowl and top with chicken or shrimp and pour broth around noodles.
3. Top with any or all of the following garnishes: bean sprouts, cucumber, Thai basil, carrots, spring onions, coriander, shallots, chili pepper or chili sauce. Squeeze a lime over soup for a zesty finsh, if desired.