Break into the coconut and remove the flesh. Chop the red chillis. Place the coconut and the red chillis in a hot, dry frying pan and cook over a high heat until golden brown. Remove from the heat, allow to cool and then place in a food processor and blend to a fine paste.
Slice the chicken breast as thinly as possible across the breast. Pick and finely chop the coriander, setting aside a quarter to use as a garnish. Zest and juice the limes. Tear the oyster mushrooms down to bite size pieces.
Place the chicken stock in a large saucepan, bring to the boil and then reduce to a simmer. Add the shrimp paste, tamarind, ground coriander, remaining fresh coriander, lime leaves, palm sugar, coconut milk and the coconut and chilli paste to the pan and simmer for 5 minutes. Add the chicken, oyster mushrooms and lime zest and juice to the soup and cook for a further 3 minutes (longer if the chicken has not been thinly sliced).
Peel and finely slice the shallots and then coat in a mixture of flour and salt. Place the sunflower oil in a saucepan and heat over a medium heat. Add the shallots to the pan and cook until crisp and golden. Remove from the oil and pat with kitchen towel to remove excess grease. Once dry, toss the shallots with the remaining coriander.
Ladle the soup into bowls and top with the crispy shallots. Serve immediately.
«This hot and sour soup can easily be adapted to taste and works equally well with seafood or tofu. Try topping with ground roasted rice as well as the shallots.»