Tom yum prawn noodle soup

Ingredients

• 60g dried soba noodles, egg noodles or quick-cook noodles
• 1 chicken, fish or vegetable stock cube, made up to 700ml
• 2 tbsp tom yum paste
• 2 garlic cloves, finely sliced
• 1 stick of lemongrass, trimmed and chopped
• 1 green chilli, deseeded and finely sliced
• 75g baby button mushrooms, sliced
• 1 x 180g pack raw peeled king prawns
• 1 tsp Thai fish sauce
• pinch of light muscovado sugar
• 2 spring onions, trimmed and finely sliced
• juice of ½ lime, plus wedges to serve
• ½ x 31g pack coriander, leaves only, roughly chopped