Toast the sesame seeds in a dry pan over a medium heat for 2 to 3 minutes, shaking often, until they smell nutty and turn pale gold. Tip them onto a plate.

Pat the chicken dry. Toss with the beaten egg, then with the 4 tbsp cornflour, plain flour and salt until evenly coated.

Whisk the soy sauce, hoisin, honey, rice vinegar, brown sugar, sesame oil, garlic and ginger in a bowl. Mix the 1 tsp cornflour with the cold water in a separate cup.

Heat the oil in a wok or wide frying pan over a high heat. Fry the chicken in two batches for 5 to 6 minutes each, turning once a crust has formed. Drain on a wire rack.

Pour off all but a teaspoon of oil. Add the sauce mix and simmer for 1 to 2 minutes.

Stir the cornflour slurry and pour it in. Simmer for 30 seconds until glossy and thick enough to coat a spoon.

Take the pan off the heat. Add the chicken and two thirds of the sesame seeds and toss to coat. Scatter over the rest of the seeds and the spring onions, then serve.