How to Make Umami-Rich Dashi Stock from Kombu and Katsuobushi

The secret to a great pot of dashi comes down to one temperature rule: never let the water reach a rolling boil while the kombu is still in the pot. Soak the kombu in cold water, heat gently until tiny bubbles form at the bottom of the pot (around 60°C, before boiling), then lift the kombu out. Only then raise the heat close to boiling (around 85°C), add the katsuobushi, and turn off the stove. Get these two steps right and you get a clear, golden, delicately sweet broth without a single grain of MSG.

This article walks you through the whole process: a refined first stock (Ichiban Dashi) for soups, a robust second stock (Niban Dashi) for simmered dishes, and a ready-made shiro dashi solution for busy days in Saigon.

What Dashi Is and Why It's the Heart of Japanese Cooking

Dashi is the foundational stock of the Japanese kitchen, widely regarded as the core of umami (a deep, savory, naturally meaty sweetness). From miso soup and oden to udon noodles and dashimaki rolled omelet, dashi shapes the flavor of most of the Japanese dishes you know.

What makes it fascinating is that this deep savoriness comes not from sugar or bouillon powder, but from a synergy between two natural compounds:

• Glutamic acid (glutamate), abundant in kombu kelp.
• Inosinate (IMP), plentiful in katsuobushi bonito flakes.

Taste science has proven it: when glutamate and inosinate meet, the perceived umami doesn't add up, it multiplies, becoming roughly 7 to 8 times stronger than either ingredient alone. This isn't addition, it's multiplication. Glutamate was discovered by Professor Kikunae Ikeda in 1908 when he extracted it from kombu; his student Shintaro Kodama later identified inosinate in bonito flakes, and the synergy itself was clarified by scientist Akira Kuninaka. The Japanese had been using this principle in their bowls of dashi for centuries before it ever had a scientific name.

Once you understand this, you can see why just two humble dried ingredients create a depth of flavor that no industrial seasoning fully replicates.

First Stock (Ichiban Dashi): 3 Steps to a Crystal-Clear Broth

Ichiban dashi yields a clear, lightly fragrant, elegant stock. It's the one to use for dishes that need to showcase pure flavor: clear soups (osuimono), broth-based bowls, and steamed egg custard. A working recipe for about 1 liter of stock: 10g kombu, 20 to 30g katsuobushi, 1,000ml water.

Step 1: Soak the kombu. Gently wipe the surface of the kombu with a damp cloth; don't scrub it. The white powder on the surface is exactly what creates umami, and washing it off takes the good flavor with it. Place the kombu in a pot of cold water and soak for 30 minutes to 1 hour.

Step 2: Heat and lift the kombu at the right moment. Turn the heat to low and warm slowly until tiny bubbles start rising from the bottom of the pot (around 60°C, before boiling), then remove the kombu right away. This is the decisive step: if the water goes above 70°C with the kombu still in, the kelp releases alginic acid, which turns the stock bitter, slimy, and cloudy.

Step 3: Add the katsuobushi, then strain. Bring the water close to a boil (around 85°C), turn off the heat, add the katsuobushi, and do not stir. Let it sit for about 2 to 3 minutes so the flakes settle, then strain slowly through a cheesecloth-lined sieve. Do not squeeze or press the solids, which keeps the stock clear and free of astringency. The result is a golden, crystal-clear broth.

An easy way to remember the proportions: the combined weight of kombu and bonito flakes lands at about 1% of the water.

Second Stock (Niban Dashi): Reuse the Solids, Waste Nothing

Don't rush to throw out the kombu and bonito flakes from the first batch. They still hold plenty of umami for a second, more robust stock that suits dishes with bolder seasoning.

• Put the used kombu and katsuobushi from the ichiban dashi into a pot with about 500ml of fresh water.
• Bring to a boil, then lower the heat and simmer for 3 to 5 minutes.
• Turn off the heat, add a pinch of fresh bonito flakes (about 4 to 5g) to boost aroma, wait 1 to 2 minutes, then strain gently.

Niban dashi is stronger and less refined, but it's the perfect choice for miso soup, simmered dishes (nimono), and hot pot broth, dishes that need a solid base flavor rather than clarity.

Busy Day? Use Granulated Dashi or Ready-Made Shiro Dashi

Making dashi from scratch delivers the best flavor, but you won't always have the time, especially with the busy schedules of the Japanese community in Ho Chi Minh City. Two popular convenient solutions:

• Granulated dashi (顆粒だし): just stir it into hot water and you have instant stock. Quick and easy for a rushed meal. The downside is that the fresh bonito aroma and clean finish are hard to match a handmade batch.
• Shiro dashi (白だし): a ready-made concentrated stock with a pale, light color. Its biggest advantage is that it preserves the natural fresh color of vegetables, eggs, and other ingredients, without darkening the dish the way ordinary soy sauce does. The flavor is pre-balanced, so you just dilute it to the right ratio for restaurant-level results.

Within this group, Yamaki Shiro Dashi (500ml concentrate bottle) is worth considering: concentrated, light in color, with the signature katsuobushi aroma preserved, and ready to use for many dishes with just a bit of dilution.

Shiro Dashi Dilution Ratios (Reference)

The ratios below are given as shiro dashi : water and can be adjusted to taste (always prioritize the instructions printed on the product you're using):

Dish	Shiro Dashi : Water
Clear soup (osuimono)	1 : 8 to 1 : 10
Noodle broth (udon, soba)	1 : 8 to 1 : 10
Simmered dishes (nimono)	1 : 6 to 1 : 8
Steamed egg custard (chawanmushi)	1 : 5 to 1 : 6, then mix with egg per package instructions

For chawanmushi, after diluting the shiro dashi you beat it together with egg (the egg-to-stock ratio is usually around 1 : 3), then steam over low heat so the surface turns out smooth and free of pitting.

Where to Buy Dashi Ingredients in Ho Chi Minh City

For Japanese residents living in Saigon, the hard part isn't the recipe, it's gathering all the right ingredients. You can check directly on the Farmi App to see whether Yamaki Shiro Dashi 500ml, kombu kelp, and katsuobushi are in stock and order the whole set in one go. [TODO: confirm SKU in the Farmi catalog — Yamaki Shiro Dashi 500ml / Kombu / Katsuobushi; mark TBD if not yet listed]

Why order through Farmi instead of hunting through Japanese supermarkets:

• ✅ Authentic and reassuring: Japanese products with clear sourcing, so you can cook with peace of mind for the whole family, true to the spirit of Home is Here.
• ⚡ Fast delivery within 1 hour in Ho Chi Minh City: in time for dinner without scheduling a shopping trip.
• 🇯🇵 Japanese-language support: browse and order as easily as you would back home.

Download or open the Farmi App now to order your dashi ingredients and receive them within 1 hour in Ho Chi Minh City. In just a few taps you'll have the kombu, katsuobushi, and shiro dashi you need to season a light, restaurant-quality umami right in your own kitchen.