Mushroom Manchurian

First, clean 280 g mushrooms and cut them into halves or quarters.
In a small bowl, whisk 3 tablespoon plain flour, 3 tablespoons cornflour, Sea salt (to taste), ground black pepper (to taste), and 6 tablespoons water into a thick paste.
Add the mushrooms to the batter and mix well until coated.
Deep-fry the mushrooms*. Preheat 1 litre oil in a deep-fat fryer or deep kadai/wok. Once it heats (lower the tip of a wooden spoon into the oil; if the oil bubbles around it, your oil is ready), carefully lower the mushroom pieces into the oil. Fry in batches until golden brown and drain on kitchen paper.
In a small bowl, combine 2 tablespoon chilli sauce, 1 tablespoon dark soy sauce, and 1 tablespoon ketchup. Set aside.
In a small bowl, whisk 1 tablespoon cornflour with 2 tablespoons water until you achieve a thick paste. Set aside.
Heat a large kadai or wok over medium heat until steaming. Add 1 tablespoon oil and quickly stir-fry 10 cloves garlic, 2 spring onions, 1 tablespoon ginger, 2 green chillies, and 2 coriander stalks (all minced) for a few seconds, until fragrant. Add the minced 10 g bell peppers and 20 g onion, and toss again.
Add the stir-fry sauce to the pan and stir. Add 200 ml water to adjust the consistency and let it bubble.
Stir in the cornflour slurry. Keep stirring continuously to avoid lumps and achieve a beautifully thick Manchurian sauce. Simmer until glossy, then add the mushrooms and toss in the sauce.
Serve hot garnished with spring onion greens.