Ingredients

Step by step

1. Toast the sesame seeds in a large frying pan or wok until golden, then set aside. Slice the sirloin steak against the grain into thin 0.5cm strips. Put 1 tablespoon of cornflour in a bowl, then toss through the strips of steak until coated all over. Prepare a steamer for the pak choi and make sure all your ingredients are prepared before the next step.
2. Heat 1½ tablespoons of oil in the same frying pan or wok. Once the oil is very hot, sear the steak strips for 1-2 minutes on each side (in two batches, if necessary), until crispy. Use tongs to transfer to a plate.
3. Allow the pan to cool for a few minutes. Meanwhile, mix together the brown sugar, 2 tablespoons of hot water and the soy sauce in a bowl. Add a further ½ tablespoon of oil to the pan, if necessary, followed by the garlic, ginger, chilli flakes (if using) and spring onion whites, then stir-fry for 1-2 minutes over a medium-low heat, until fragrant. Pour in the sugar-soy mixture, then bring to the boil and bubble for 2 minutes. Meanwhile, stir together 1 teaspoon each of cornflour and cold water until combined. Add the pak choi to the prepared steamer and cook for 4-5 minutes, until tender.
4. Stir the cornflour slurry into the pan, followed by the beef. Heat through for a final 2-3 minutes, until the sauce is a syrupy coating consistency. Serve the beef with rice and the steamed pak choi, then scatter with the spring onion greens and toasted sesame seeds to serve.