Begin by preparing your marinade ingredients: keeping the skin on, grate your Asian pear, then peel and mince your garlic and ginger, and finely chop your spring onion. Add all to a large mixing bowl along with the rest of the marinade ingredients and mix well, making sure that the sugar fully dissolves.
Next, peel and finely slice the white onion half, and leave to one side to be used later.
Now, prepare your steak. Cut the meat into thin slices, and tenderise further by bashing the pieces with the side of a knife or cleaver. Then, add the steak to the bowl of marinade mixture, and use your hands to massage the marinade flavours deep into the meat. Leave the steak to marinate in the fridge overnight, or at least for one hour if pushed for time.
When ready, set your wok over a high heat and add 1-2 teaspoons of vegetable oil. Swirl the oil around the wok to try and baste the entire inside cooking surface, then bring to smoking point. Once the oil is smoking, arrange the slices of steak piece by piece around the edge of the wok, leaving a gap in the middle. Crank the heat up to its highest to sear the meat, then add another swirl of oil to the gap in the middle of the wok followed by the sliced white onion.
Keeping the heat high, use the back of your ladle to push into the meat and onions, allowing them to sear on one side. Once the underside is showing a deep golden brown colour, then flip over and sear on the other, beginning to stir-fry if the meat begins to stick or burn. Then, add the rest of the marinade liquid to the wok, stir-frying for just 2 minutes until the sauce wraps around the meat, but the beef is not overcooked.
Remove the wok from the heat and serve the completed beef bulgogi with steamed rice and fresh, stir-fried vegetables, if desired.