1. First make the puris. Stir the flours and salt into a large bowl. Add 2 tbsp sunflower oil and rub it into the flour with your fingertips until well mixed in. Stir in the cumin seeds.
2. Gradually mix in the cold water to make a soft, slightly sticky dough, then turn it out on to a well-floured work surface and knead for 5 minutes. Rub the ball of dough with a little more oil, drop into a clean bowl, cover and leave for 30 minutes.
3. Knead the dough again for about 3 minutes until smooth. Divide the mixture into 12 even-sized balls, dust each one quite heavily with flour then roll out into 12.5cm/5in discs.
4. Heat oil to a depth of 2.5cm/1in in a large saucepan or deep-fat fryer until it reaches 190C/375F. Fry the puris one at a time for 1 minute on each side until puffed-up and golden brown. Drain on kitchen paper and keep warm in a low oven while you cook the prawns.
5. For the coconut chilli prawns, heat the oil in a large pan. Add the ginger and garlic and fry for 30 seconds. Add the curry paste and fry for a further 2 minutes until it looks like it is splitting away from the oil.
6. Add the prawns to the pan and stir-fry over a high heat for 3 minutes until firm and pink. Add the creamed coconut and hot water and stir every now and then until the coconut has melted. Simmer for 1 minute.
7. Mix the coriander with the red chilli and spring onions. Stir into the prawns and serve immediately with the cumin puris.