Crisp Cod and Potato Fish Cakes with Lemon-Herb Mayonnaise

Boil and dry potatoes. Cover the potato chunks with cold water in the large saucepan, bring to the boil and simmer for 15-20 minutes, until a knife slides in without resistance. Drain well, return them to the hot pan for 2 minutes to steam off excess moisture, then mash until smooth and leave to cool for 10 minutes. Dry mash is the backbone of a firm cake, since watery potato makes the mixture slump.

Poach the fish. Lay the fish in the shallow pan with the milk and bay leaf, so the milk reaches about halfway up the fillet. Over medium-low heat, bring it to a bare simmer, cover and cook for 6-8 minutes until the flesh is opaque throughout, flakes easily and reads at least 63°C at the thickest point. A gentle poach keeps the fish moist instead of tight and stringy; lift it onto a plate with the slotted spoon, discard the milk and bay, and cool for 10 minutes.

Fold the mixture. Break the fish into large flakes, checking carefully for bones as you go. Tip it into the potato along with the spring onions, parsley, lemon zest, beaten egg, salt and pepper. Fold gently rather than beating, so plenty of chunky flakes survive and the cakes have real texture.

Shape and chill. With wet hands, form 8 cakes roughly 7cm wide and 2.5cm thick and arrange them on the lined tray. Chill for at least 30 minutes, or cover and keep for up to 24 hours. Cold cakes are firmer, so they hold their shape when they hit the hot pan.

Coat in crumbs. Set out the flour, beaten egg and panko in the 3 shallow dishes. Dust each cake in flour, dip it in egg, then roll it in panko, pressing the crumbs on firmly. The flour gives the egg something to grip, and the egg glues on an even, unbroken crust.

Fry until golden. Heat the oven to 200°C (fan 180°C). Warm 2 tbsp of the oil in the frying pan over medium heat and fry 4 cakes for 3-4 minutes per side, until deep golden, then transfer them to the baking tray. Repeat with the remaining oil and cakes; medium heat browns the crumbs without scorching them before the cakes are handled.

Bake through. Bake the cakes for 8-10 minutes, until the centre of one reads at least 71°C on the probe thermometer, which matters because the mixture contains raw egg. Finishing in the oven heats the middle evenly while the crust stays crisp rather than over-browning in the pan.

Mix the mayonnaise. While the cakes are in the oven, stir the mayonnaise with the lemon juice, chives and parsley until evenly flecked with green. The sharp lemon cuts through the richness of the fried crust.

Plate up. Serve 2 cakes per person with a spoonful of the mayonnaise, a handful of salad leaves and wedges cut from the zested lemon. Eat straight away, while the crumb is at its crunchiest.