Prawn skewers with peanut dipping sauce

INGREDIENTS

• 1kg large, raw prawns , with shell on (about 30)
• oil
• 1 tbsp ground coriander
• 1 tbsp ground cumin
• a large pinch of turmeric
• palm sugar or soft light brown sugar 100g
• 2 fresh or dried, small red chillies , finely sliced
• 4 kaffir lime leaves , finely shredded (optional) or zest of 1 lime
• 5 tbsp roasted, unsalted peanuts , finely chopped
• ¼ of a cucumber , seeded and finely chopped