Place the sliced beef into a bowl and sprinkle over the bicarbonate of soda. Toss to coat and leave for 20 minutes to tenderise.
Rinse the beef under cold water to remove the bicarbonate of soda, then shake off any excess water.
In a bowl, mix together the soy sauce, hoisin sauce, mirin, honey and sesame oil. Spoon about 1½ tablespoons over the beef and toss to coat.
Stir the cornflour into the remaining sauce until smooth, then mix in the water.
Heat the oil in a large frying pan or wok over a high heat. Add the carrot and stir fry for 2–3 minutes so it starts to soften.
Add the onion and garlic and cook for about 10 seconds until fragrant.
Add the beef and stir fry for 1–2 minutes until it just starts to brown.
Add the red pepper, pak choy and spring onions. Stir fry for another minute.
Pour in the sauce and stir well. It will bubble and quickly thicken into a glossy coating.
Serve straight away with rice. Finish with sesame seeds or a drizzle of crispy chilli oil if you like.