Dashi is Japanese for soup stock. It comes in all sorts. Hon dashi (本だし) is never vegan as it’s fish stock. Konbu (こんぶ – kelp) and shiitake dashi are more promising, but they usually contain bonito (also call katsuoboshi), a fish product.
There are at least two brands of Japanese instant konbu dashi which are vegan. The first is made by Shimaya (シマヤ), comes as mid-green sachets (long and thin) in a green plastic bag, and is labelled こんぶだしの素. I have also seen the same product in boxes. You might read that this product contains lactose—it used to, but doesn’t any more. If you want to check, go to the product page and search for 乳糖, which is Japanese for lactose. You’ll find it in the shiitake dashi (which used to be vegan—poo!), but not the konbu dashi at the top. The ingredients translate as:
seasonings (amino acid etc), table salt, saccharides (dextrose, sugar), natural flavourings (kelp powder, kelp extract). You can get this from the Japan Centre, or any of the Japanese supermarkets in London.
The second is a similar product made by Ajinomoto, and is packaged almost identically, with eight long and thin, but light green, sachets per pack. When I first spotted it, I thought it was the Shimaya one with re-vamped packaging. The ingredients for this brand are
salt, sugar, mannitol (E421), monosodium glutamate (E621), powdered kelp, kelp extract.
There are two more brands, which are vegetarian, but unfortunately aren’t vegan, though for one of them you’d never tell from the translated ingredients list. Riken Mutenka (“additive-free”) Konbu Dashi is also GM-free. The importer translates the ingredients as simply “tangle”. The actual list is:
flavourings (kelp extract, powdered kelp), starch, lactose, yeast extract. The other is a Dutch macrobiotic brand, Manna, which also contains lactose (I thought macrobiotics discouraged the use of dairy?).
If you know you will need the dashi a few hours in advance, it’s simple but time-consuming to make your own. Good dashi konbu will be thick and not too wrinkled – I’ve had consistently good results with the Korean Wel-Pac brand, which is stocked by pretty much all Chinese supermarkets and is easy to obtain. To make a litre of stock, take a sheet and break it into three long pieces. Wipe the konbu with a damp cloth and place in a large pan with a litre of water. Put the lid on the pan and bring quickly to the boil, then reduce the heat and simmer until you have about ¾ of the original volume of liquid. If your pan lid does not have a hole in it to let steam out, place it ajar whilst simmering. Top up the water back to the original level, using cold water, and simmer for a further 20 minutes or so, then top up again and simmer for another 10 minutes.
By this point you will know if you had good quality konbu as it will have expanded and small blisters will appear on the surface. The more dashi you make, the longer it will take to cook. It will keep for a few days in the refrigerator, and you could consider making a highly concentrated version and freezing it—just use less water or more konbu.
Another trick for simmered dishes is to simply place a piece of dashi konbu at the bottom of the pan before you add the other ingredients and remove it after cooking. Don’t throw the used konbu away, though, as it is still good to eat.