Speedy sweet potato soup with coconut

INGREDIENTS

• 1 tbsp vegetable oil
• 1 onion , chopped
• 1-2 tsp Thai curry paste , red or green
• 1l vegetable stock
• half sachet creamed coconut (or ¼ can reduced-fat coconut milk)
• handful coriander , roughly chopped
• mini naan bread , to serve
• 750g sweet potatoes , grated