Peel the potatoes, then cut into very thin matchsticks and place in a large bowl with 2 teaspoons salt. Cover with cold water and leave to stand for 8–10 minutes. Drain thoroughly and pat dry with kitchen paper.
Heat the oil a large nonstick wok or frying pan over a high heat. Add the garlic, fresh ginger, pickled ginger and chilli flakes and stir-fry for about 30 seconds. Season with salt and white pepper, then add the potatoes and gently stir-fry for a minute or so until well coated with the spices and flavourings.
Add the sugar and rice wine and continue to stir-fry for about 8–10 minutes until most of the water has evaporated and the potatoes are tender. Add the chilli oil, scatter over the Szechuan pepper and serve immediately.