- Combine fish, potato starch, 1 tbsp vegetable oil and 1 tbsp water in a bowl. Mix well to combine and marinate for 20 mins.
- Heat 300ml vegetable oil in a wok over high heat until smoking. Add doubanjiang, black beans, spring onion, half the dried chilli and two-thirds of the Sichuan peppercorns, reduce heat to medium and cook until oil turns red, then add garlic, ginger and Shaoxing wine and stir-fry until fragrant. Add stock, 13-fragrance spice powder, season to taste with white pepper and caster sugar and simmer, stirring occasionally, until well-flavoured. Add fish mixture, reduce heat to low and simmer until fish is just cooked. Add soybean sprouts, cook until just wilted and transfer to a serving bowl.
- Wipe out wok and return to medium-high heat. When smoking, add chilli oil and remaining vegetable oil and heat to 160ºC. Add remaining dried chillies and remaining Sichuan peppercorns and stir-fry until fragrant, then pour over fish and serve hot.