Here are some roughly scraped dried fish flakes. It's a mixture of mackerel, sardines, and horse mackerel. You can use mackerel flakes if you'd like. I bought this for 258 yen per 150 g at a supermarket.
Add mirin to a saucepan and boil over medium heat to evaporate the alcohol.
Add soy sauce and bring it to a boil. Put the mixed flakes in a tea bag because they release scum, then add to the saucepan.
Simmer for 10 minutes over low heat. You MUST simmer this. After 10 minutes, turn the heat off and set aside to cool down. That's it.
For homemade nametake mushrooms, simmer enoki mushrooms in this all-purpose soy sauce with vinegar, and sugar. Recipe ID: 1236025.
This will keep for 2 weeks in the fridge.
Story Behind this Recipe
Because store-bought mentsuyu doesn't have a strong umami flavor, I made this homemade mentsuyu using mackerel flakes. They are used for a very strong umami flavor to make soba dipping sauce.
The mentsuyu noodle dipping sauce you get at soba restaurants uses mackerel flakes; that's why it's so tasty. These flakes give out so much umami flavor. If using this as mentsuyu, make sure to dilute it as follows: Pouring sauce - 1 part all-purpose soy sauce: 4-5 parts water Dipping sauce - 1 part all-purpose soy sauce: 2-3 parts water.