2 cups vegetable broth
250g (1 cup) prawn tails, shelled and deveined
1 handful coriander
2 red chillies, halved down the middle
3 kaffir lime leaves
1 stick lemongrass, tied in a knot
1 large tomato, cut into wedges
1 black mushroom, sliced
1 tbsp hot Thai chilli jam or paste
juice of 1 lime
1 tbsp fish sauce