Heat the oil in a large pan over a medium heat and cook the mustard and cumin seeds for 3-4 mins until they start to pop. Add the curry leaves, onion, garlic, chillies (if using) and a large pinch of salt. Stir and cook for 10-12 mins until just softening. Stir in the fenugreek seeds, being careful not to let them burn. Add the tomatoes, curry powder, turmeric, tamarind and 200ml water. Stir, then pour in the coconut milk. Bring to a simmer. Bubble for 15 mins until thickened.

Meanwhile, for the mash, tip the potatoes into a pan and cover with cold water and a large pinch of salt. Bring to the boil and cook for 17-20 mins until tender. Drain and leave to steam-dry. Mash using a masher or potato ricer, or pass through a fine mesh sieve, if you like.

Heat the oil in a pan over a medium heat and cook the onions and cumin seeds for 10 mins until the onions are soft. Add the garlic, ginger, turmeric and a large pinch of salt. Cook over a medium-low heat for 5 mins more, stirring. Stir in the cream. Slowly stir the masala cream into the mash.

Heat the oven to 220C/200C fan/gas 7. Put the spinach in a sieve and pour over a kettle of boiling water. Cool, then squeeze out the excess water. Stir the spinach into the curry with the fish pie mix. Transfer to a baking dish and spoon or pipe over the mash. Bake for 20-25 mins until golden on top and crisp at the edges.

Meanwhile, for the peas, heat the oil in a frying pan over a high heat and cook the onion for 8 mins, stirring until caramelised at the edges. Reduce the heat to medium-high. Add the garlic, ginger, curry leaves, spices and 1/2 tsp salt. Add the peas and cook for 5 mins until tender. Keep warm over a low heat.

Remove the pie from the oven and leave to rest for 10 mins. Serve with the devilled peas on the side.