Put a litre and a half of water into a saucepan with the salt, and put over a medium heat. Heat, stirring, until the salt has dissolved, then pour into a cold bowl and leave to cool while you prepare the cabbage.

While the brine is cooling, wash the cabbage and chop it lengthways into quarters. Carefully cut out and discard the woody core from each quarter, then cut the quarters into thick slices about 4cm wide.

Put the cabbage slices in a large bowl and pour over the cooled water, tossing so all the leaves come into contact with the brine. Leave to sit at room temperature, turning occasionally, until the tough white stems have wilted, which will probably take two to three hours.

Wash and cut the radish and carrot into bite-sized cubes. Sprinkle with two teaspoons of salt, leave to sit for half an hour, then drain. Wash and roughly chop the spring onion.

Crush or finely chop the garlic, ginger and salted shrimp, if using. Put these in a bowl with the chilli flakes, sugar and fish sauce, if using, mix well and loosen with 150ml cold water.

Rinse the cabbage very well under cold water, washing in between the leaves to get rid of any salt still clinging on, then drain thoroughly. Shake the leaves dry in a clean tea towel, then tip back into the large bowl. Pour in the seasoning and toss to coat.

Spoon the kimchi into a clean jar, crock or pot, pressing it in very firmly to minimise the amount of air trapped between the leaves. Seal the jar.

Put the jar in a cool place out of direct sunlight for five days, checking on it and pushing it back down under the liquid as necessary. Once it’s sour enough for your taste, refrigerate it to pause the fermentation process.