Peel the ginger and carrots and cut into small cubes. Cut the celery into small pieces. Chop up the chives and coriander. Peel and crush the garlic clove.
Add all the ingredients for the broth into a pot and fill with 1L of water. Bring the pot to the boil and and let it cook for 5 minutes. When done, let it rest with lid on.
Cut the steaks longways into slices (approx. 1 cm thick). Then lightly fry in a hot pan with some olive oil
Cook the soba noodles according to the instructions given on the packet (usually about 5 minutes in water).
Cut the spinach leaves into strips, the spring onion into rolls and the mushrooms into slices.
Divide the finished soba noodles among the bowls for serving, add some spinach, mushrooms, spring onions and the steak slices on top and pour some broth over the top.