Cut the chicken breasts into 1.5 cm (¾ inch) cubes. Mix the turmeric with the salt, rub into the cubes of chicken and leave to stand for 30 minutes.
Bruise the lemon grass with the side of a rolling pin to release the flavour. Finely crush the roasted peanuts in a food processor or using a pestle and mortar. Heat a dry frying pan and toast the rice until golden brown, then finely crush to a powder in a food processor or spice grinder.
Heat the oil in a large pan and fry the onion until just softened. Add the chicken together with the garlic, ginger, lemon grass, paprika and chilli. Add the fish sauce and measurement water and bring to the boil.
Reduce the heat to a simmer. Mix together the crushed peanuts and ground rice and add to the pan. Simmer for about 10–15 minutes or until the chicken has cooked through and the broth thickened slightly.
Stir the noodles into the pan and heat for 1 minute.
Ladle the chicken soup into bowls and serve garnished with the hard-boiled eggs, chopped coriander and shredded spring onions. Add an extra splash of fish sauce, to taste.