Coconut & Chicken Broth

1.2 L chicken broth 

100g mushrooms, sliced 

2 sticks lemongrass, roughly chopped 

4 cm piece ginger, grated

1 red chilli, roughly chopped 

400ml coconut milk 

1 tbsp fish sauce

1 tbsp lime juice, plus wedges to serve 

1 handful fresh coriander, roughly chopped