Gochujang fish pie with sweet potato and black sesame

Method

1. Cook the potatoes in salted boiling water until soft (around 20 minutes), then lift out with a slotted spoon and set aside to steam dry. In the same pan of boiling water, cook the eggs for 6½ minutes, then drain and transfer to a bowl of cold water to stop them from cooking further.
2. Meanwhile, pour 500ml boiling water from the kettle over the stock cube, stir to dissolve and set aside. (If using fresh stock, cook it in the microwave on high for 1 minute to warm through). Put 50g of the butter in a large saucepan over a medium heat and, once melted, stir in the flour to make a paste. Cook, whisking, for 2 minutes to cook out the floury taste, then slowly whisk in the hot fish stock bit by bit, to avoid lumps. Stir in the gochujang paste and vinegar, then season with a pinch of salt and pepper and leave to cool slightly.
3. Drain the potatoes, leave to steam dry for a minute, then return to the pan and mash with the remaining butter. Season with a big pinch of salt. Heat the oven to 180ºC fan/gas 6.
4. Stir the fish, prawns (if using), peas and spinach into the sauce and transfer to an ovenproof dish. Peel and halve the eggs, then nestle them into the sauce. Spoon over the sweet potato mash, spread to cover, then sprinkle with black sesame seeds and put in the oven for 30 minutes. Serve with a spoonful of crunchy kimchi on the side.