When you look across high end Japanese cuisine, specifically at their counter dining culture, you’ll most likely be familiar with how the phrase omakase literally means ‘I leave it up to you’, implying that the customer trusts the chef to all aspects of the dining experience. From the flow of the meal, all the way to the choice of season ingredients and dishes served. At most places, even the tableware and seating plans are decided by the chef beforehand.

However, often overlooked is the chef’s judgment of the seasoning of the dish. At a sushi restaurant, the chef applies his choice amount of wasabi and soy sauce into each piece of nigiri. Even for yakitori, the skewers are seasoned with tare during the grilling process. Here, the sweetness and saltiness of the tare is determined by the chef. 

This is where tempura differs.*

What is Tentsuyu

Other than the choice of oil which flavors the tempura slightly, no additional salt or soy sauce is added to tempura and any seasoning is left up to the customer. This is most commonly done by dipping tempura into a sweet and salty sauce known as tentsuyu (天つゆ). In Japan, dipping sauces in general are called tsuyu and so tentsuyu is specific to tempura (ten- for tempura).

As such, preparation of a high quality tentsuyu complements the dining experience if you are trying to serve quality tempura.

Whilst less common, restaurants that hail from the kyoboshi school of tempura serve it with lemon and salt instead of tentsuyu. 

Alternatives to homemade tsuyu

Straight off the bat, we want to say that there are many high quality pre-made tentsuyu sauces that you can buy online or in the grocery store that taste significantly better than most recipes on the internet. Therefore, if you’re short on time they can be valid alternatives. As with most recipes on this site, we are introducing a more complicated version of a tentsuyu recipe that we believe to yield better results.

Ingredient ratios for homemade tentsuyu

While there exists small variations from recipe to recipe, you’ll find that most of them adhere to a version of a 4:1:1 ratio of dashi, soy sauce and mirin. We also recommend using hon-mirin if you can obtain it. If you want to learn more, read our article on ingredient ratios. 

You’ll notice that this recipe does not call for sugar as mirin is already naturally sweet. The addition of sugar to tsuyu is actually far more common outside of Japan, especially in the US where people have become more accustomed, or even desensitized to sugar and thus expect a hint of sweetness in the sauce. People sometimes use sugar to also mask the use of inferior ingredients such as mass produced soy sauces or artificial mirin. 

If you’d like to add some sweetness to tsuyu, start by adding in a small amount of sugar to begin with, stirring it in while hot until dissolved. Taste and repeat to your taste. 

Some restaurants choose to add brown sugar instead of white sugar as they prefer a more caramelized taste that they feel matches the richness of tempura batter.

What makes this recipe special

When you look at tsuyu recipes on the internet you’ll find that most of them use dashi stock as a base. Shortcut versions will simply use powdered dashi while more complicated versions might make dashi directly from kombu and katsuobushi flakes.

What sets this recipe apart from other tsuyu recipes on the internet is that katsuobushi is added at two different times in the process, once before boiling and once after. This second addition further fortifies the savoriness of dipping sauce in exchange for a higher cost as double the amount of katsuobushi flakes are used. 

What this does is layer the flavors by first extracting the savory and smoky notes of the katsuobushi during the initial boil, before adding in the more delicate earthy and nutty aromas that would otherwise be boiled away. 

The recipe below is based on 500ml water. This may seem like a large amount, but it is so that a more meaningful amount of katsuobushi can be weighed out and measured. Extra tentsuyu produced by this recipe can be frozen or stored in the fridge for up to a week. 

Reusing old tentsuyu

Whilst tentsuyu can be stored in the fridge for at least a week, some restaurants will opt to add their remaining unused tentsuyu from a previous batch to deepen the flavor of the new batch. Sauces like these are known as ‘living’ sauces in Japan and are similar to how teriyaki, unagi and anago sauces are treated. Doing this helps to build a depth of flavor to the sauce as certain compounds break down and oxidize overtime. It is safe to do so long as the sauce is brought up to a boil after every addition of a previous batch’s sauce. 

Serving tentsuyu with tempura

Tentsuyu is usually served at a cold temperature, either with or without grated daikon added into it. Therefore, your tentsuyu should be kept refrigerated until just before serving. 

While rare to find, there are instances of people serving tentsuyu with grated ginger or even grated umeboshi instead of daikon. 

Restaurant Tentsuyu recipe

10g of kombu (around 25cm² in size)

30g of katsuobushi (15g of the initial addition and 15g for the secondary)

500ml of water

125ml of soy sauce

125ml of mirin

Add water to a pan with the kombu. Allow to soak for 30 minutes to an hour if time permits, otherwise skip. Allowing to soak leads to a more savory sauce.

Heat the pan just until small bubbles start to form on the bottom of the pan, or until it registers 80°C with an instant-read thermometer.

Take off the heat and remove the kombu, then add katsuobushi, and leave to infuse for one or two minutes.

Strain the stock through a muslin cloth or cheesecloth, layered across a fine meshed strainer and allow to drain naturally. Do not squeeze the cloth to extract more dashi. This squeezes out impurities from the flakes.

Add the mirin and soy sauce to the liquid and bring to a boil. If using a large flame, be careful as the evaporating alcohol from the mirin might catch fire. 

Boil for 1 to 2 minutes to evaporate the alcohol. Alternatively, set the alcohol alight using a match. 

Switch off the heat and add the second addition of katsuobushi flakes whilst still hot.

When the katsuobushi flakes have sunk to the bottom and infused for a few more minutes, strain and cool in the fridge before serving. 

Notes:

*Of course you occasionally get sashimi served with salt or soy sauce and yakitori served with a side of wasabi or horseradish, but they’ve already been seasoned beforehand. Even the sashimi should have been salted. If you want to see a unique example of a tempura restaurant that seasons their tempura before serving, read our article on Tempura Kusunoki.