Remove and discard the fat from the sirloin and slice into thin 1-2” strips against the grain. Put the meat in a bowl with the corn starch. Stir until the meat is coated, then fold in the soy sauce, sesame oil and the rice wine. Put in the fridge to marinade for 15 minutes at least.
Remove the outer leaves from the head of cabbage, and wash the cabbage. Shake off the rest of the water and break off the leaves. Cut out the thick white heart of each leaf and cut the remaining frill into inch-square pieces.
Heat a pan over medium high to high heat and add half the peanut oil. Take the strips of meat out of the marinade, shake off the moisture as well as possible and fry them in the pan on both sides, in small batches, about 1 minute per side. Put the meat aside in a bowl and cover.
Add the rest of the peanut oil to the pan and when it’s hot, put in the garlic, ginger and green onions. Stir-fry quickly until the onions begin to brown, then add the meat back in, together with the meat juices from the bowl. Quickly add the cabbage and stir-fry for 30 seconds. Then add the oyster sauce and stir in quickly. Serve immediately.