1.5 litres (2 1/2 pints) hot chicken or fish stock
2 cm (3/4 inch) piece of fresh root ginger
1 lemon grass stalk
2 kaffir lime leaves
1 teaspoon brown sugar
1 tablespoon Thai fish sauce
400 g (13 oz) oyster mushrooms, sliced
250 g (8 oz) raw large prawns
lime juice, to taste
handful of chopped fresh coriander, to garnish
Heat a large, heavy-based saucepan. Add the curry paste, then stir in the stock, ginger, lemon grass, lime leaves, sugar and fish sauce. Bring to the boil, then reduce the heat and simmer for 5 minutes.
Add the mushrooms and prawns and season to taste. Cook for a further 3–4 minutes until the prawns are just cooked through. Add lime juice to taste, remove the ginger, lemon grass and lime leaves if liked, and serve immediately, scattered with the coriander.