Donal Skehan's spice bag chicken buns

Name: Donal Skehan's spice bag chicken buns
Cuisine: Asian, Chinese
Ingredients: 8 skinless chicken thigh fillets, cut into strips; 400ml buttermilk; 100g corn flakes; 2 tbsp plain (all-purpose) flour; Pinch ground white pepper; Sunflower oil spray; 2 tbsp vegetable oil; 1 red chilli, thinly sliced; 6 spring onions (scallions), thinly sliced diagonally; 1–2 tbsp Shaoxing wine (or use rice wine); 1 tbsp sesame oil; 4 brioche buns, lightly toasted; 1 gem or 1⁄2 iceberg lettuce, shredded; 1 tbsp Chinese five-spice; 1⁄2 tsp garlic powder; 1 tsp chilli powder; Pinch ground cardamom; Pinch cinnamon; 2 tsp salt; 2 tsp granulated sugar; 1⁄2 tsp white pepper; 1 egg yolk; 1 clove of garlic, grated; Pinch salt; 1 tbsp rice wine vinegar; 125ml neutral oil; 1 tbsp fish sauce; Small handful coriander, finely chopped