Prepare the vegetable soup broth. Place 1.2 L (0.3 gallons) of water and the vegetables into a pot, turn on the heat and once boiling simmer over low heat for 30 minutes. Strain with a strainer placed over a bowl to prepare 800 ml (27 fl. oz.) of soup broth. If less than desired volume, add water as required.

Place the strained vegetable soup broth from (1) into a pot, bring to a boil and adjust the taste with (A).

Cut the Japanese onion in half lengthwise, then slice each half open lengthwise and layer the sliced halves. With the grain, slice up into ultra-fine strips, place these in water for 5 minutes and then drain.

In a separate pot boil water to cook the noodles. Pour the soup from (2) into bowls, add in the boiled noodles then top with the Japanese long onion strips.