Fill the kettle and boil it. Peel and finely chop the onion. Pop in a pan with 2 tbsp hot water from the kettle. Cover. Cook over a low heat for 5-8 mins till soft. Stir every so often. If it looks like it’s sticking, add a splash more water.
Peel and grate or crush the garlic. Add to the onion with 1 tsp of the turmeric and 1 tsp of the garam masala. Cook and stir for 1 min.
Stir in the tomatoes. Pour in 150ml hot water from the kettle. Bring to a boil. Cover and simmer for 5 mins.
While the sauce simmers, halve the cauliflower and rinse it. Roughly chop one half into chunks. Pop in a food processor. Blitz for 1-2 mins to make cauliflower ‘rice’.
Rinse the watercress. Pat dry. Pull off any large stalks so you just have smaller, tender stems and leaves. Put to one side.
Chop the whiting into bite-sized pieces. Add to the pan. Cover and cook gently for 5 mins till the fish flakes easily. Taste and season with salt and pepper. Put to one side, with the lid on.
Tip the cauliflower into a pan. Pour in 100ml hot water from the kettle. Cook over a medium heat for 4-5 mins till just tender. Drain, if necessary. Season. Serve topped with the watercress and curried whiting.