Ingredients

Step by step

1. Bring the milk, thyme sprigs and paprika to a gentle simmer in a wide pan. Add the cod and prawns, remove from the heat and leave to poach for 4 minutes. Scoop out carefully onto a plate, reserving the milk.
2. Heat the oil in a frying pan and cook the chorizo for 5 minutes. Add the onions and cook for 10 minutes. Sprinkle over the flour and stir until it is absorbed.
3. Add the poaching milk a splash at a time (transfer to a jug or use a ladle), continually stirring until it’s completely incorporated. Simmer on a low heat, continually stirring, until thickened and smooth – about 5-10 minutes (you want it fairly thick at this stage, as the fish will release more liquid during cooking). Remove from the heat, season and add the fish and prawns to the sauce (don’t stir too much or the fish will flake up).
4. Melt the butter in a small pan with the saffron, take off the heat and leave to infuse.
5. Heat the oven to 200°C, fan 180°C, gas 6. Cut the potatoes into slices 2-3 mm thick (you can use a mandoline if you have one), discarding the two rounded ends. Blanch in a large pan of boiling salted water for 5 minutes, then drain in a colander, trying not to break them up. Leave to steam dry.
6. Spoon the fish mixture into an ovenproof dish about 25cm diameter (or a 20 x 30cm rectangular dish), then layer the potatoes on top, slightly overlapping, in a spiral or in lines. Brush over the saffron butter, season and bake for 30 minutes until the potatoes are cooked and light golden. Grill for the last few minutes to crisp up the potatoes if you like.