In a small bowl, blend cornflour smoothly with soy sauce. Stir in stock and set aside.
Heat a wok or large non-stick frying panover a high heat, add oil and heat for 30 seconds. Add pork and stir-fry for 5 minutes, until cooked through and no longer pink. Place on a paper towel on a plate.
Add garlic and onion to wok, cook, stirring constantly, for 2 minutes. Add broccoli and capsicum, cook, stirring constantly, for 2 minutes, until tender-crisp.
Add pork and soy sauce mixture to wok. Cook, stirring constantly, until the mixture boils and thickens, and the pork is heated through. Stir in cashews, heat for 1 minute. Place rice onto individual warmed dinner plates, spoon pork mixture over rice, serve immediately.