Whisk all sauce ingredients together and set aside. Toss the steak with the brown sugar and cornflour, then season well with salt and pepper.

Heat 2 tablespoons of the oil in a large wok or frying pan. When hot, cook the beef for 2-3 minutes until browned. Transfer to a plate while cooking the vegetables.

Add the remaining oil to the pan along with red pepper, spring onion whites, ginger, and chilli. Cook, stirring often for 2 minutes.

Add the green beans and mushrooms, cooking for a further 2 minutes. Stir in the sauce and cover, cooking for 4-5 minutes until softened.

Return the beef and any resting juices to the pan, cooking for 2 minutes while tossing to combine. Transfer to a serving platter.

Scatter the peanuts, sesame seeds, and spring onion greens over the stir fry and serve immediately with steamed rice.