Rub salt on pork and let it sit overnight in the fridge.
Put water, ginger root, garlic, green onions and salted pork in a pot, and boil at high heat. Skim fat and other floating scum. Then cover, reduce to low heat, and simmer for 1 1/2 to 2 hours. (Or cook in a pressure cooker for 20 minutes. ) Let the broth and pork cool completely in pot. Strain and save the separated broth and pork.
Let the broth cool in the fridge at least a couple of hours or overnight, and then remove the solidified fat. Keep cooked pork in the fridge too so that it can be easily sliced later.
Prepare the rest of the toppings now as well (boiled eggs, blanched bean sprouts, cut green onions), before making the soup and noodles. Once the noodles are cooked, you will need to add the soup and toppings right away or the noodles will get soft, so you won't have time to prepare the toppings then.
Boil the broth and add soy sauce, sake, salt and sesame oil. Let it simmer at very low heat until the noodles are ready.
Cook dried Chuka dried noodles according to the package. Just before the noodles are done, pour the soup in serving bowls. Strain water from the noodles and immediately divide the noodles into the serving bowls.
If you are using dried thin spaghetti: In boiling water in a pot, add baking soda (be careful, it may boil over), then the spaghetti. Cook the pasta according to the package, and strain. Immediately divide noodles into bowls with the soup.
Top with boiled eggs, bean sprouts, green onions and sliced pork.