Slice the chicken breasts into thin, flat pieces or cubes. Place them in a bowl and season with salt, black pepper powder, vinegar, light soy sauce, and ginger garlic green chilli paste. Mix well to coat.

Add corn flour, refined flour, and egg white to the chicken. Mix thoroughly to coat the chicken pieces evenly.

Heat oil in a pan over high heat. Once the oil is moderately hot, carefully add the chicken. Fry on medium-high heat until golden brown on both sides. Transfer the fried chicken to a sieve to drain excess oil.

In a wok, melt butter over high heat. Add roughly chopped garlic, green chili, and chopped coriander stems (or celery). Stir and cook for 2-3 minutes over medium heat without browning the garlic.

Pour hot water into the wok and stir. Season with a pinch of salt, light soy sauce, vinegar, black pepper powder, and sugar. Cook over high flame for 2-3 minutes.

Mix corn flour with water to make a slurry. Add this to the wok and stir continuously until the sauce thickens.

Add the fried chicken, lemon juice, lemon zest, and spring onions to the wok. Toss well to coat the chicken in the sauce.

Garnish with spring onion greens and serve hot.