Kerala prawn curry

INGREDIENTS

• 2 red chillies split, cut into quarters lengthways and seeded
• 1 small red onion , chopped
• 2.5cm piece of fresh root ginger , peeled and chopped
• 1 tbsp vegetable or sunflower oil
• 1 tsp black mustard seeds
• ½ tsp fenugreek seeds
• 14 curry leaves , fresh or dried
• ½ tsp turmeric
• ½ tsp cracked black peppercorns
• 250g jumbo prawns , leave some with their tails on if you like
• 150ml reduced-fat coconut milk
• a squeeze of lime
• chopped fresh coriander , plus a sprig or two
• freshly boiled basmati rice