Tom Yum Soup

Ingredients

• 1 litre (4 cups) chicken stock or water
• 2 stalks lemongrass, bottom 15cm only, bruised and cut into 3cm pieces
• 4 slices fresh galangal (or 3cm piece fresh ginger, sliced, as substitute)
• 4 kaffir lime leaves, torn in half (fresh or frozen)
• 3–4 bird's eye chillies, bruised (adjust to heat preference)
• 200g (7oz) raw prawns, peeled and deveined (or chicken breast, thinly sliced)
• 150g (5oz) oyster or straw mushrooms, halved
• 3 tablespoons fish sauce, or to taste
• 2 tablespoons fresh lime juice (about 2 limes)
• 1 teaspoon sugar (palm sugar or caster)
• 2 tablespoons nam prik pao (Thai roasted chilli paste) — for the creamy version
• 100ml (7 tablespoons) coconut milk (optional, for the creamy version)
• 1 tomato, cut into wedges (optional)
• 1 small bunch fresh coriander, to garnish
• 2 spring onions, sliced, to garnish