Combine the beef, lemongrass, onion, garlic, ginger, chilli and five-spice in a large bowl.
Heat ¼ of the macadamia oil in a wok over high heat until just smoking.
Add ¼ of the beef mixture and stir-fry for 2 minutes or until the beef is browned.
Transfer to a bowl. Repeat in 3 more batches with remaining beef mixture and oil, reheating wok between batches.
Heat the sesame oil in the wok. Add the beef mixture, oyster sauce, chicken stock and broccolini and stir-fry for 1-2 minutes or until heated through.
Remove wok from heat. Add the macadamias and half the basil and toss to combine.
Spoon stir-fry among serving bowls. Sprinkle with remaining basil and serve immediately with steamed rice.