What is Dashi?
Dashi is Japanese style stock and can be source from Asian grocery stores in teabag style bags or powder form (it is hard to find organic varieties... we are working on stocking this in our shop) but you can make them yourself too! It is not essential to use dashi for miso soup but can definitly enhance the flavour by adding umami. For more on how to make miso soup click here.
Dashi in Japanese cuisine are mainly made from three ingredients - katsuobushi (dried and fermented bonito flakes), kombu seaweed, and dried shiitake mushroom and it is good to combine more than one of them to add more umami to your dashi and there is a reason for it.
Umami has three main components; glutamate, inosinate and guanylate. Glutamate can be found in a variety of foods including meat, fish and vegetables. Glutamate is very rich in seaweed, as well as vegetables, mushrooms and cheese. Inosinate can be found in animal-based foods such as meat and fish and increase when fermented. Guanylate can be found in dried mushroom products such as dried shiitake. It is scientifically proven that umami is sensed far more strongly when glutamate is combined with inosinate or guanylate so the combination of kombu (glutamate), katsuobushi (inosinate) and dried shiitake (guanylate) is absolutely genious!
Here are some information on how to make dashi the traditional way (but not necessarily essential in making miso soup - for more click here).
Katsuobushi (Bonito Flakes)
Katsuobushi, also known as Okaka, is dried and fermented bonito fish flakes. It is made by filleting the fish, boiling, smoking (12-15 times over a month) and fermenting with a fungus called Aspergillus glaucus (same family as Koji fungus) and sun-drying repeatedly for up to two years until it resembles a rock hard piece of wood. Inosinate increases during the fermentation process. It is then shaved into flakes before used in cooking. You can buy shaved katsuobushi at Asian groceries.
To make dashi, boil water in a pot until you see small bubbles and then turn heat off and add the Katsuobushi flakes (10g to 1L of water). Wait until the flakes sinks to the bottom of the pot and then strain using a paper towel lined sieve and you have your golden dashi.
Kombu is sold in dried or powdered form and can be used to make vegetarian dashi. There are two ways of making dashi with kombu and you need about 10g of Kombu to 1L of water.
You can add dried Kombu in cold water and slowly heat until near-boiling. Kombu should be removed at this point to prevent dashi from becoming slimy. You can get a stronger dashi if you soak kombu in the water for about 30 minutes before you turn the heat on.
The other way is to soak kombu in cold water overnight. When you do this you can also add dried shiitake to it to make a more flavoursome vegetarian dashi.
The Kombu used to make dashi has lots of nutrients so please don't throw away. You can slice and simmer it with soy sauce and mirin on its own or with other vegetables.
If kombu is difficult to source, you can try with other leafy seaweed. We at Rice Culture use organic Tasmanian Wakame which produces a very umami rich dashi.
Dried Shiitake Mushroom
Mushrooms are very rich in glutamate, but when dried some mushrooms such as shiitake, porcini and morel also produces guanylate which, when combined with gulamate rich food enhances the umami flavour.
To make dashi with dried shiitake, add 40-50g of shiitake to 1L of water and leave in fridge overnight. You can use this as stock but to make a more umami rich dashi, slowly heat up the water with shiitake in it until you see small bubbles (ideally taking 15 - 20 minutes to reach this stage) and turn the heat off and strain the liquid. Don't boil the water as it will deactivate the enzymes that produces the umami and add bitterness to the dashi.
The shiitake used in making dashi can be used in cooking so don't throw away. Dried shiitake mushroom is a great source of Vitamin D.