Slice the tofu into rectangular, bite-sized chunks. Drain and pat dry with kitchen paper to get rid of any excess moisture, then season with a good pinch of sea salt and freshly ground black pepper.
Heat 1cm of groundnut oil in a large wok over a medium heat. Drop a small piece of tofu into the hot oil – if it sizzles and turns golden, it’s ready to go. Add the tofu in batches and fry for 5 to 8 minutes, or until golden, turning regularly.
Meanwhile, toast the cashew nuts in a dry frying pan for 1 to 2 minutes, or until golden. Tip into a pestle and mortar and crush lightly. Peel the garlic and deseed the chillies, then finely slice. Slice the pak choy lengthways into quarters, then halve each piece lengthways again. Trim and slice the spring onions into 2cm pieces.
Once golden, use a slotted spoon to remove the tofu to a double layer of kitchen paper to drain. Carefully remove and discard most of the oil, leaving about 1 tablespoon in the pan, then return to a medium-high heat. Add the garlic and chilli and fry for 1 minute, or until lightly golden, then add the pak choy and spring onions. Fry for a further 3 to 4 minutes, or until softened slightly. Stir in the mirin, soy sauce, honey, sesame oil and vinegar for 1 minute and give it another good stir. Throw in the cashews and fried tofu, toss well for a minute to warm through, then serve straightaway.