The $6 ingredient to elevate your Japanese cooking, according to a top chef

The one ingredient you need in your kitchen to elevate your Japanese cooking?

When you ask chef Alex Yu this question, he doesn’t hesitate: kombu.

“You can’t talk about Japanese cuisine without talking about kombu,” Yu says. “It is fundamental. It’s at the very, very base and core of Japanese cuisine.”

If you’ve dined at a Japanese restaurant or cafe, you’ve almost certainly eaten kombu. An edible kelp, it’s widely consumed across East Asia, but is a particular feature of Japanese cuisine, used in dashi, sushi rice, hot pots and udon noodles.

But the riddle, Yu says, is that kombu doesn’t actually have much taste itself.

So what makes it so important? Its ability to enhance the flavour of the ingredients it accompanies; and that’s because of its concentration of glutamic acid, which imparts the taste of umami, which is so prized in Japanese food.

“It depends on what you want, but it has this subtle but very deep flavour, which means it helps feature other ingredients, in a sense,” he says.

Yu shows me some sheets of kombu he uses as executive chef at Sokyo Brisbane (Yu was previously head chef at Yugen in Melbourne, and before that Sokyo Sydney).

They’re enormous, their matte black texture dusted with dried salt. Yu’s kombu is sourced from Korea, and the type he uses depends on import restrictions that sometimes come and go with Japanese products.

“There are other places you can get it too, but the seas where this is from are quite close [to Japan],” he says.

Yu says he’s seen sheets of kombu that sell for “easily $200” in Japan, and that the grading tends to indicate how much umami you can extract from it in your cooking.

But it needn’t be expensive, with a 25-gram pack of sheets going for as little as $6 at the local Japanese grocery store.

How to use it at home? There are plenty of ways, Yu says, including pickling it and putting it on rice, chopping it and adding it to sauce, or dampening the kombu sheet and using it to wrap a piece of fish for four to six hours.

“All that flavour goes into the fish, giving it a different texture and flavour,” he says.

Still, dashi is the killer app, particularly when you’re using it to make miso soup.

“The best way to [cook it] is in water that’s about 60 degrees Celsius – so a little more than hot – and then you take it off the heat and skim all the excess foam and debris. And then you’re commonly adding katsuobushi, or bonito flakes.

“The glutamic acid of the kombu and acetic acid of the bonito have a synergistic effect, meaning the umami level multiplies significantly,” Yu says. “It’s why a good miso soup has that huge depth of flavour.”