Hot and sour fish soup

Name: Hot and sour fish soup
Cook time: 20 min
Total time: 20 min
Cuisine: Asian, Thai
Ingredients: grated to make 2 tbsp ginger; ½ red chilli finely chopped; 2 spring onions thinly sliced; 1 stalk lemongrass lightly bashed; 700ml light chicken stock; 3 tbsp soy sauce; 2 tbsp rice vinegar; 400g skinless firm white fish cut into chunks; 2 handfuls baby spinach chopped; 2 tsp Thai fish sauce; to serve (optional) cooked rice or rice noodles