First make the stock. Cut the turkey carcass into manageable pieces and crush the coriander seeds with a pestle and mortar. Place them in a large saucepan, add 1.2 litres (2 pints) of water and all the other ingredients. Bring it to the boil, reduce the heat to low, cover the pan and simmer for 35-40 minutes.
Meanwhile, finely chop the turkey breast.
Remove and discard the largest pieces of turkey carcass from the stock then strain the stock through a large sieve into a measuring jug. There should be 750 ml (1 pint 7 fl oz); if not, add water to make up the amount.
Put the coconut milk powder in a large saucepan and pour the measured stock onto it. Place the pan over a medium heat and whisk the stock and milk powder to eliminate any lumps.
When the coconut mixture begins to bubble, reduce the heat to low and add the turkey and chilli, and salt to taste.
Blend the cornflour with 1-2 tablespoons of cold water, add it to the soup and stir for 2-3 minutes until the soup thickens.
Add the fresh coriander, stir briefly, remove the soup from the heat and serve, garnished with a chilli in each bowl, if you wish.
Variation: you could also make the stock with the carcasses of two large chickens.