Curried fish pie topped with Bombay potatoes

Method

1. Put the potatoes in a large pan of salted water and bring to the boil. Simmer for 10-12 minutes until tender, then drain.
2. In the same pan, add the butter and melt over a medium heat. Add the mustard and nigella seeds, cook for 1 minute until fragrant, then return the drained potatoes to the pan and roughly mash with a fork, leaving some chunks. Stir in the coriander and a pinch of salt, then remove from the heat and set aside.
3. Heat the oven to 180°C fan/ gas 6. For the filling, heat the oil in a large frying pan and gently cook the onion for 3-5 minutes until starting to soften. Stir in the cauliflower florets and curry paste, mix well, then pour in the coconut milk. Add the chopped spinach, then cook for 6-8 minutes, stirring occasionally, until thickened and the cauliflower is tender. Season to taste with salt and set aside.
4. Stir the fish pie mix into the filling, then transfer to an ovenproof dish (see Make Ahead). Spoon the potato mixture on top, then cook in the oven for 25 30 minutes or until golden and crisp on top. Cut the lemon in half and squeeze over the pie before serving.