Meanwhile, heat wok over high heat until hot. Add 2 teaspoons of oil and swirl to coat. Add half the beef. Stir-fry for 1 minute or until sealed. Remove to a plate. Repeat with oil and remaining beef.
Add remaining 1 tablespoon of oil to wok. Add onion, capsicum and garlic. Stir-fry for 2 minutes or until vegetables are tender. Return beef and any juices to wok. Add choy sum, peanut butter, coconut cream, sweet chilli sauce and oyster sauce. Stir-fry for 2 to 3 minutes or until choy sum is tender and stir-fry heated through.
Divide rice between bowls. Top with stir-fry. Sprinkle with chilli. Serve.