In a bowl, combine 4 tablespoons soy sauce, 1 medium garlic clove (minced, or 1 teaspoon garlic powder), and 2 tablespoons flour. Coat 4 chicken breasts in this mixture until fully covered. Refrigerate for 30 minutes. At the same time, soak 25g Mu-Err mushrooms in lukewarm water.
Bring a pot of water to a boil and blanch 1 small head broccoli (florets and tender stalk pieces) for 2-3 minutes until tender-crisp, then drain. Using a vegetable peeler or julienne cutter, slice 2 medium carrots thinly. Cut 1 bunch spring onions into thin rings. Slice 1 medium yellow bell pepper into thin strips.
Heat 4 tablespoons oil (such as sesame oil) in a wok over medium-high heat. Add 100g unsalted cashew nuts and toast for 1-2 minutes, stirring constantly. Add the marinated chicken with its marinade and fry for 5 minutes while stirring constantly, until the chicken is cooked through (internal temperature 74°C/165°F).
Add the blanched broccoli, sliced carrots, spring onion rings, and bell pepper strips to the wok. Stir-fry for 2-3 minutes.
Drain the soaked Mu-Err mushrooms and cut into small pieces. Add them to the wok along with the drained bamboo strips. Stir-fry gently for 2-3 minutes more, keeping vegetables as crisp as possible. Season to taste with soy sauce, oyster sauce, sugar, and fresh chilli.
Serve with Chinese egg noodles or rice. Optional: top with a spoonful of sambal oelek.