For the marinade, place the rice wine or sherry, soy sauce, honey, orange juice and ground pepper into a large bowl and whisk well to combine. Add the beef steaks, cover the bowl with cling film and leave to marinate for 10-15 minutes in the fridge. Heat a wok until smoking and add the groundnut oil, then add the steaks, reserving the marinade. Fry for 1-2 minutes on each side for rare, 2-3 minutes for medium, or longer for well-done. Transfer the steaks onto two serving plates, cover with foil and leave to rest for five minutes. Pour the reserved marinade into the wok and cook over a high heat for 30 seconds, or until the sauce is sticky. Add the shiitake mushrooms to the wok and cook for 3-4 minutes, or until the mushrooms are softened. Add a splash of water to help create some steam to cook the mushrooms. To serve, remove the foil from the plates and spoon the mushrooms alongside the steaks. Garnish with the orange segments and spring onion and serve with mixed salad leaves.