Heat the vegetable oil in a large saucepan, add the kimchi, onion, garlic and ginger, and stir-fry for 5 minutes.
Stir through the gochugaru and gochujang, then add the mushrooms, 2 litres (68 fl oz/8 cups) water, sea salt and a good grind of black pepper. Bring to the boil and simmer, uncovered, for 25 minutes.
Slice the tofu into 1-cm (½-in) slices. After the mixture has cooked for 20 minutes, taste it and adjust the level of salt if needed. Place the tofu on top of it, spoon some of the sauce over it, and cook gently for a further 5 minutes. Top with the spring onion, and serve immediately.
Alphabet Cooking: K is for Korean (Quadrille, £12) Photography Kim Lightbody
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