Making Kombu Dashi
This is the simplest way to understand the baseline of Japanese cooking. You are looking for a gentle extraction that avoids the sliminess and bitterness that come from over-boiling the kelp.
Mind the white powder.
The white, dusty coating on the surface of the kombu is mannitol, which carries significant flavor. Wipe it only if it is sandy; do not wash it off under running water.
- Heavy-bottomed pot
- Soft cloth or paper towel
What goes in.
- 4 cupscold water
- 1 piece (approx 4-inch square)dried kombu
Stop before the boil
Remove the kombu just as the water begins to shimmer and small bubbles form at the edges. If the water boils, the stock will become cloudy and develop a mucilaginous texture.
The method.
Soak the kombu
Wipe the kombu gently with a dry cloth. Place it in a pot with the cold water and let it sit for at least 3 hours, or overnight in the refrigerator.
Heat gently
Place the pot on the stove over medium-low heat. Bring the water slowly toward a simmer.
Extract
Watch the edges of the pot closely. When you see tiny bubbles starting to rise, pull the kombu out immediately with tongs.
Finish
Use the dashi immediately or store it in a sealed container in the refrigerator for up to three days.
Other turns to take.
Quick Extraction
If you are short on time, simmer the kombu on the lowest heat setting for 10 minutes without letting it reach a boil, though the cold-soak method yields a cleaner taste.
When it doesn't go to plan.
Do not discard the used kombu; slice it thinly and simmer it with soy sauce and mirin for a side dish.
Use soft water if possible; hard water can prevent the mineral-rich kombu from releasing its full profile.
If you have a digital thermometer, pull the kombu when the water reaches 140°F (60°C).
The ones that keep coming up.
Why did my dashi turn slimy?
The kombu was likely boiled or left in the water for too long after heating. Remove the kelp before the water hits a rolling boil.
Can I reuse the kombu for a second batch?
A second, lighter extraction is possible by simmering the used piece in fresh water, but it will lack the intensity of the first soak.
How real cooks make it.
No one’s shared their version yet. Be the first to put your kitchen on the map.
Cook this your way?
Share your version — your steps, your story. We’ll feature it right here.
Add your recipe