When you buy the beef, don't put it in the refrigerator - leave it at room temperature. If the meat is too cold when you cook it, the inside will be raw. ("Rare" and "raw" are not the same thing.) Beef that's just before the best-by date is tastier than fresh beef. If you find some Aussie beef round as shown here that's on sale at half price, it's a must buy!
Put aromatic vegetables like celery, onion, Japanese leek, carrot, parsley, Chinese cabbage, regular cabbage etc. (celery and leek are a must, if you have bamboo shoot skins that's great!) into a pot with the water, and bring to a boil.
If the Aussie beef block you bought came with a spice packet, rub it into the meat. If it didn't come with anything rub with salt and pepper (not listed). Be generous with the pepper.
Brown the meat in a pan. Be sure to use high heat.
When the pot of vegetables from step 2 comes to a boil, put in the beef! Bring back to a boil, and cook over high heat for 1 minute! Turn off the heat, dissolve the salt in the water, leave for 12 to 15 minutes and then take out the beef only. The cooking time varies depending on the size of the meat blocks, 15 minutes is OK in most cases!
If you're worried about whether the meat is cooked enough, try cutting off an edge. If it's light pink in the middle it's great! (If you touch the middle and it's cold, then it's raw.) It's delicious as-is, but if you put the meat back in the cooking liquid for an hour once the liquid has cooled down to about 120°F/50°C, it will absorb the flavors of the vegetables and become even more delicious!
If there are any leftovers or if you're not going to eat the beef right away, keep the cooking liquid in storage bags or containers, where it will keep for 3 to 4 days in the refrigerator.
Slice the beef as thinly as you can when serving. To be honest it's cheaper and healthier than ham, so use it in salads and sandwiches and eat a lot of it.
Use storebought salad dressing, mustard, wasabi soy sauce, grated daikon radish and ponzu sauce, or whatever other sauces you like with the beef. Here's an easy sauce recipe: mix store-bought yakiniku sauce with ponzu soy sauce in equal amounts.
Story Behind this Recipe
Roast beef made in an oven is often either undercooked or overcooked... and beef that's raw on the inside is tataki, not roast beef. This recipe is for boiled beef rather than roast beef maybe? Nevertheless, I came to this method as a way of ensuring that the beef is cooked to the right degree of doneness.
If the meat is too cold when you start cooking it, it will be raw on the inside so be careful! As I wrote in Step 1, bring the meat to room temperature or as close to it as possible before you start cooking it! Even if the meat doesn't have a good color right after it's cut, it will look nicer after a short time. You can use whatever vegetables you like except for potatoes in the cooking water, but I personally think you have to have celery and leek. Bamboo shoot skins are a great addition, but they are seasonal.