Rinse the 300g jasmine rice in cold water, swirling it with your fingers and changing the water 2–3 times, until it runs mostly clear, then drain well. Combine the rice, 450ml water and the small pinch of salt, if using, in a saucepan and bring to a boil over medium-high heat. Cover tightly, reduce to very low heat and cook for 12 minutes, then take it off the heat and leave it to rest, still covered, for 10 minutes before fluffing with a fork; a rice cooker works just as well with the same quantities. Start the marinade as soon as the lid goes on, so the rice is ready before the wok heats. That measured 1:1.5 ratio and covered rest are what keep the grains fluffy and separate rather than heavy or wet under the stir-fry.

Put the 800g bite-size chicken thigh pieces in a bowl and add the 1 tbsp light soy sauce, 1 tbsp oyster sauce, 1 tsp fish sauce, 2 tsp cornstarch, ¼ tsp white pepper and 1 tsp neutral oil. Mix thoroughly with your hands or a spoon for about 30 seconds, until every piece is evenly coated and no dry cornstarch remains at the bottom of the bowl. The chicken should look lightly glossy rather than wet. Leave it to sit for 15 minutes while you prepare the sauce and vegetables. That thin cornstarch-and-oil coating is what keeps the thigh meat juicy in the fierce heat and gives each piece a smoother stir-fried surface for the sauce to cling to.

In a small bowl, whisk together the 3 tbsp oyster sauce, 2 tbsp light soy sauce, 1–1½ tsp dark soy sauce, 1 tbsp fish sauce, 2 tsp brown sugar or palm sugar, 120ml chicken stock or water and 2 tsp cornstarch, adding the 1 tsp chilli jam if using, until the sugar and cornstarch have dissolved. Set it aside. Cut the red and green bell peppers into bite-size chunks and the onion into medium wedges or thick slices, not thin strips. Finely chop the 5 garlic cloves, slice the 3 scallions on a bias and pick the cilantro. Break the dried chillies into pieces if using, and keep the 120g cashews within reach. That complete preparation matters because the stir-fry moves fast and genuinely cannot wait while you chop.

Heat a large wok or wide heavy skillet over high heat until it is very hot and a drop of water sizzles away instantly. Add 1–1½ tbsp of the neutral oil, swirling it around the pan. Add half the chicken in a single layer and leave it largely undisturbed for 2–3 minutes, until the undersides are lightly browned, then stir-fry for another 2–3 minutes, until mostly cooked through with light browning at the edges. Lift it onto a plate and repeat with the second batch, adding a little of that oil first if the pan looks dry. The pieces should look genuinely distinct and glossy, not pale and sitting in liquid. That batch searing is what keeps the wok hot enough to brown the chicken instead of steaming it.

Return the wok to high heat and add the remaining 1–1½ tbsp neutral oil. If using the dried chillies, add them first and stir-fry for 10–15 seconds, just until fragrant and darkened slightly, never blackened. Add the chopped garlic and stir quickly for 10 seconds, then add the onion and stir-fry for 1 minute. Add the red and green bell peppers and stir-fry for 1½–2 minutes, tossing constantly, until they are slightly softened but still genuinely vibrant and a little crisp at the centre. If the garlic starts to brown too fast, lift the wok off the heat for a moment. That short, hot cooking is what keeps the vegetables colourful and lightly crisp rather than collapsing into the sauce.

Return the chicken and any juices from the plate to the wok. Stir the prepared sauce again to lift the settled cornstarch from the bottom of the bowl, then pour it in. Toss continuously for 1–2 minutes, until the sauce thickens, turns glossy and coats the chicken and vegetables, and the thickest piece of chicken reaches 74°C / 165°F with no pink at the centre. The sauce should cling with a shine, neither pooling thinly like soup nor turning pasty; stop as soon as it looks right. Add the 120g cashews and about two-thirds of the scallions and toss briefly, just to combine. Turn off the heat and fold in a little of the cilantro, keeping most of it for garnish. That late addition is what keeps the cashews distinct and crunchy.

Fluff the rested jasmine rice once more and divide it among 4 bowls, giving each a generous bed. Spoon the cashew chicken over the top so every bowl gets about 200g of chicken, a share of red and green peppers and onion, plenty of cashews and enough sauce to coat rather than flood the rice. Scatter over the remaining scallions and cilantro. Serve immediately, while the vegetables are still crisp and the cashews still crunchy. That quick assembly is what lets the rice catch just a little of the glossy sauce while every component stays genuinely distinct and visible in the bowl.