For the chicken, mix the egg white with the potato flour in a bowl, then add the soy sauce, Shaohsing wine (or sherry) and the chicken. Turn the chicken over to coat it.

For the sauce, mix together the tomato purée, 2-3 tbsp water, potato flour, soy sauces, rice vinegar, sugar and Shaohsing wine and set this aside. Snip the chillies into 5cm lengths, discarding the seeds.

Heat the oil in a wok and cook the garlic, ginger and chillies over a medium heat until they’re aromatic and beginning to soften, but not brown.

Mix the cornflour and plain flour for the coating with salt and pepper and tip into a broad shallow bowl. Working with one piece of chicken at a time, dip it in the flour mix and set the pieces onto a tray.

Pour enough oil into a deep pan to come 8cm up the sides. Heat until it reaches 200C (if you drop in a test piece of chicken, it should sizzle straight away). Carefully add half the chicken pieces and fry until they’re crisp and golden – agitating the pieces to make sure they don’t stick together – about 4 mins. Lift the pieces out with a slotted spoon onto a double layer of kitchen paper. Repeat with the rest of the chicken.

Heat the wok, add the sauce mixture to the garlic, ginger and chillies in there and cook, stirring, until the mixture bubbles and thickens. Add the chicken and half the spring onions and warm everything through. Serve with the sesame seeds and the rest of the spring onions scattered on top. This doesn’t give you huge servings so it’s best to offer another dish with it, as well as boiled rice.