Combine the chicken, garlic, salt, wine, and 1 teaspoon cornstarch (cornflour) in a large bowl, then add the oil and marinate for 10 minutes.
Put the cashew nuts into a wok or large skillet (frying pan) and add enough oil to cover them completely. Heat the oil to 285°F/140°C, or until a cube of bread turns golden in 2 minutes. Deep fry the nuts for 2-3 minutes, or until crunchy. Use a slotted spoon to carefully remove the nuts from the oil and drain on paper towels.
Pour out most of the oil leaving 1 tablespoon in the wok and heat over medium heat. Add the shallots and stir-fry for 1–2 minutes until fragrant. Put in the chicken, increase to high heat, and toss rapidly for 2 minutes until browned. Add the bell pepper and soy sauce and stir-fry for another minute, or until the chicken is cooked through. Stir in the scallions (spring onions).
Mix the remaining 1⁄2 teaspoon cornstarch with 1 teaspoon water in a small bowl and stir this mixture into the wok. Bring to a boil, stirring, for about 30 seconds to thicken the sauce. Add the sesame oil and garnish with cilantro (coriander), if using. Serve with rice.