Marinate the beef in tamari for 15 minutes. Meanwhile, heat a large non-stick wok over high heat (if not non-stick, add 1 teaspoon of coconut oil, 43 calories, and carefully swirl to coat the sides of the wok).

Roughly divide the beef into thirds. Stir-fry the first batch for 1 to 2 minutes or until the beef is browned and just cooked. Transfer to a plate. Repeat with the beef in two more batches, reheating the wok (and adding a little more coconut oil if needed) between each batch.

Cooking the beef in batches is very important as it seals the meat, keeping in the juices. If you add too much meat at once, the wok will lose its heat and the meat will stew and become tough.

Remove all the meat from the wok. Add the spring onions and stir-fry for 3 minutes or until tender, adding the bok choy in the last minute. Add back the beef and toss together. Season with cracked pepper to serve.