Peel the sweet potatoes and cut into 1 cm cubes. Cut the onions into strips.
Put the coconut milk in a saucepan, add the chilli, bay leaves, lemon juice, turmeric, stock powder and onion strips and bring to the boil. Add the sweet potato cubes and cook everything for about 10 - 12 minutes, until the sweet potatoes are just tender.
Divide the fish fillet into approx. 2 cm pieces and add to the sweet potatoes. Let simmer again for about 5 minutes.
Stir in the Asian fish sauce and season the stew with salt and freshly ground pepper.
Arrange on plates and sprinkle with fresh parsley.