Fish and chips

Peel the potatoes and cut them into 1–1.5 cm thick batons. Rinse in cold water and dry thoroughly with a towel.

The potatoes must be completely dry: water hitting hot oil makes it spit violently.

Pour the oil into a deep pot, filling it no more than halfway, and heat to 160 °C.

No thermometer? Dip a wooden chopstick in the oil: steady small bubbles mean about 160 °C, vigorous bubbling means 180 °C. Keep a lid nearby and never pour water on burning oil.

Fry the potatoes in batches until soft but not coloured. Lift out with a slotted spoon onto paper towels.

Cut the cod into 4 portions, pat dry, season with salt and dust with 40 g of the flour. Bring the oil up to 180 °C.

Mix the remaining flour, baking powder and a pinch of salt. Pour in the ice-cold sparkling water and whisk briefly to the thickness of runny sour cream — a few lumps are fine.

Make the batter just before frying: the bubbles and the cold are what make the crust light and crisp.

Dip a piece of fish in the batter, let the excess drip off and lower it gently into the oil, away from you. Fry 2 pieces at a time for 6–7 minutes, turning, until golden; the fish should be white and flaky inside.

Lay the fish in away from you rather than dropping it, so the hot oil doesn't splash your hands.

Return the potatoes to the oil at 180 °C and fry until golden and crisp. Lift out and salt straight away.

Plate the fish and chips with lemon wedges on the side. Enjoy!