Soba and Kombu Dashi soup

Kombu dashi. I used dark soya sauce so my soup is quite dark. A light soya sauce will give a lighter soup.

I really love Japanese food. I especially love Japanese soups; they are low in fat but are warm and yummy on an autumn's afternoon.

We recently had a Japanese PhD student visiting our lab for a few months and she introduced us to a lot of Japanese food and cooking we would never have known about. And her father owns a chain of sushi restaurants in Japan so I think we can take it for granted that she knows what she is talking about!

I recently asked her for a recipe for some sort of soba noodle soup. She gave me the below recipe (to which I've added only minor comments). It involves something called kombu which is dried kelp to make the base soup. We found some in our local Asian grocer (although the packet is not necessarily going to be in English so you should ask someone). Besides from that the ingredients are pretty standard.

Kombu. An essential, pre-prepared ingredient for the soup base.

 Soba and Kombu Dashi soup

for the kombu dashi (advanced prep needed)

6 cups water

3 x 2 inch pieces of kombu

for the noodle soup

400g/14 oz. dried soba (buckwheat noodles)
1/3 cup soya sauce
2 tbsp mirin
1/2 tsp salt

for the topping

~300g block of tofu

2 tbsp sesame oil

1 leek, finely chopped

1 sheet nori, shredded

In advance:

The kombu dashi soup base can be made in 2 different ways: a quick way or a long (better) way. 

For both ways you take the kombu pieces and tear a couple of one inch tears on each end of the piece. This is to give the water somewhere newly exposed to seep in to. The piece should still be whole just with tears on each end (see picture).

Tear the ends of the kombu about 1 inch.

The long way to make the kombu dashi is to place the pieces in the 6 cups of water and soak for at least 4 hours (overnight is fine). The quicker way is to soak for 20 minutes and then slowly bring the soaking kombu to the boil. Before it starts bubbling, take it off the heat. After you've done either of these you need to strain the water to remove the pieces of kombu and anything else. To do this use a sieve and line it with 2 paper towels. Pour the liquid through the paper towels and sieve. You should collect some very clear, pure liquid at the other end. Discard the pieces and keep the clear liquid. The clear liquid is your kombu dashi.

To make the soup:

First fry the tofu. To do this you should pat your tofu block with paper towels to absorb as much liquid as possible. Then slice the tofu up into small chunks. Heat the sesame oil in a wok on high and fry the tofu for 2-3 minutes on each side. Once fried, place the tofu on clean paper towels to soak up some of the oil.

Cook your soba noodles according to the packet instructions (normally boil water, add soba, boil for 6-7 minutes, drain, rinse with cold water).

Heat the kombu dashi soup with the soya sauce, mirin, and salt in a large pot to make the soup. 

 Serve the soba noodles into four bowls. Pour the hot boiling soup over the noodles. Put the toppings on top of the noodles in each bowl.

Serves four.