Mentsuyu (Noodle Soup Base) 麺つゆ
from https://www.justonecookbook.com

Mentsuyu is Japanese soup base used in soba and udon noodle dishes. It’s made from sake, mirin, soy sauce, kombu (kelp), and katsuobushi (dried bonito flakes). Also called noodle sauce, mentsuyu is frequently added to udon, hiyamugi, somen, and other noodle meals as a dipping sauce. In Japan, it is pretty common to use mentsuyu as a dip for cold soba as it effectively enhances the taste of this popular cuisine. Because of its versatility, mentsuyu can also be used to season different kinds of dishes, including stir-fry or steamed vegetables, teriyaki, tofu, and tempura.

There are two types of mentsuyu: kaketsuyu, which is poured hot over boiled noodles to make noodle soup, and tsuketsuyu which literally means “dipping soup” for chilled noodles.

Mentsuyu is usually sold concentrated, so dilute with water before using. The proportion of water used to dilute the soup base varies depending on the use. Usually 2-3 parts of water for 1 part of mentsuyu. This mentsuyu recipe is also concentrated, so please adjust the soup base accordingly.

½ cup sake
1⅛ cup mirin
1 cup soy sauce
1 kombu (dried kelp) (2" x 2")
1 cup katsuobushi (dried bonito flakes)

Gather all the ingredients.

In a medium saucepan, add sake and bring it to a boil over medium high heat. Let the alcohol evaporate for a few seconds.

Add mirin and soy sauce. Then add kombu and katsuobushi. Cook on low heat for 5 minutes.

Turn off the heat and set aside until cool down.

Pass the mixture through a fine sieve and now Mentsuyu is ready to use.

You can store in the refrigerator up to a month.

2 cups