Mussels in Thai broth

Name: Mussels in Thai broth
Ingredients: 4 thin slices galangal, finely chopped; 1 long red chilli, seeds removed, roughly chopped; 4 coriander roots, cleaned and chopped; 2 clove garlic, roughly chopped; 1 tablespoon vegetable oil; 1 cup (250ml) chicken stock; 1 cup (250ml) coconut milk; 1 stick lemongrass, bruised; 1 tablespoon fish sauce; 1 tablespoon grated palm sugar; 1 kilogram black mussels, cleaned, debearded; 1 tablespoon lime juice; 1/4 cup coriander sprigs; crusty bread, to serve