Heat a wok over a high heat until hot. Add one tablespoon of the vegetable oil, then add the beef slices and stir fry for 1-2 minutes, or until the beef slices have browned on the outside. Transfer the beef slices to a sieve suspended over a bowl and set aside.
Return the wok to the heat, add the remaining vegetable oil, then add the cavolo nero leaves. Stir fry for 1-2 minutes, or until wilted.
Add the sliced garlic, ginger and chilli and stir fry for a further 1-2 minutes.
Add the black bean sauce and hot beef stock, stir well to coat the ingredients, then simmer the mixture over a high heat for 1-2 minutes.
Return the beef slices to the pan until heated through.
To serve, spoon the rice into the centre of four serving plates. Spoon over the stir fry and serve immediately.