Thinly slice the chicken breast fillets across the grain. Make a thin paste by mixing the salt, cornflour, egg white, sesame oil and Chinese wine or sweet sherry in a medium bowl until well combined. Add the chicken slices and stir so that they are well coated with the paste.
Heat a wok or a deep medium saucepan on high heat until very hot. Add 2 tablespoons of oil and the almonds and stir-fry for 1–2 minutes, or until the almonds are golden. Remove the almonds to a plate lined with paper towels to drain.
Heat enough oil on medium-high heat in the wok or saucepan for deep-frying – the oil is hot enough when a cube of bread dropped in begins to bubble immediately. Add the chicken, a few pieces at a time, and cook in batches until the chicken is golden. Remove to a plate lined with paper towels to drain. Repeat until all the chicken is cooked. Remove the oil from the wok or saucepan and wipe clean with paper towels.
To make the sauce, combine the cornflour, caster sugar, soy sauce and chicken stock in a jug and set aside.
Heat the wok or saucepan on high heat until hot. Add a little oil and the onion and stir-fry for 1 minute. Add the mushrooms and stir-fry for 1 minute more. Add the capsicum and the sauce ingredients and cook, stirring occasionally, until the sauce comes to the boil. Add the chicken and stir to coat the chicken with the sauce. Cook for 1–2 minutes, or until the chicken is heated through. Add the almonds and toss well to combine.
Serve the chicken and almonds over hot cooked rice garnished with spring onions.