For the kimchi: In a large bowl, rub the salt thoroughly through the cabbage, and allow it to soften and form a little brine for an hour or so. In a small cup, make a paste by combining the garlic, ginger, chilli flakes and fish sauce. Using a colander, drain the cabbage so that you retain some of the brine in a bowl. Combine the carrots and spring onions with the cabbage, and stir through the hot fishy sauce. Add a little brine if you need to loosen the mix. Spoon the kimchi into a jar, pressing down well to exclude air bubbles. Use a freezer bag part-filled with water to keep the vegetables submerged and seal the jar. Allow the kimchi to ferment for five days at room temperature. The kimchi should have a pleasingly sour taste. Leave to ferment in the fridge for a few days (or weeks) if you prefer it sourer.
For the pad thai: If using dried noodles, cook them according to the packet instructions, then drain and toss in a few drops of oil so they don’t glue together.
Make the sauce by combining the tamarind, fish sauce and sugar in a small pan; bring to the boil to dissolve the sugar. Add the chilli flakes or fresh chilli to taste and put to one side.
In a large pan, ideally a wok, heat the vegetable oil over a high heat. Add the chicken (or prawns/tofu) and the onion and stir-fry for eight minutes, until coloured and just about cooked through. Add the garlic and beaten egg to the pan for the final two minutes of stir-frying time.
Add the noodles and stir-fry for a further three minutes, making sure that the chicken is cooked through. Add half the nuts, the spring onions, kimchi and beansprouts and fry for a minute to combine.
Stir through the sauce and cook for a minute longer before removing from the heat.
To serve, sprinkle with the remaining nuts and all the herbs. Add a splash more fish sauce/chilli if you fancy and serve with the lime wedges. Add a dash of kimchi.