Step 1
Preheat the oven to 190 degrees.

Step 2
Prepare the mash by boiling the potatoes in a large pan of salted water for around 20 minutes, until they are tender. Add the cauliflower in after 15 minutes until tender at the same time as the potatoes. Mash together until smooth.

Step 3
Heat the Trex in a pan, adding the ground turmeric, onion, cumin and mustard seeds and cook for 2- 3 minutes before stirring in to the mash.

Step 4
In a separate pan, heat some oil in a pan and fry the onion until soft for 4-5 minutes. Add the garlic, chilli and ginger and cook for a further 2 minutes before adding mustard seeds, cumin, turmeric and plain flour. Cook for an additional 2 minutes. Slowly add the coconut milk and leave to simmer for 5 minutes until thickened. Stir in the fish, coriander, tomatoes and lime juice, and pour in to an oven dish.

Step 5
Spoon the mash on to the fish mixture, using a fork to make it even. Put in the oven for 35 minutes until crisp on the top. Remove from the oven and serve hot.