This is a concentrated broth often used in Japan for noodle type dishes, such as in udon, soba, etc. Many recipes can jumpstart from this basic tsuyu, such as oden, salad dressing, other types of sauces by incorporating vinegar, more sugar, ginger, garlic, miso, etc. You can buy type of tsuyu in Japan easily and nowadays most people buy bottled versions which are excellent depending on the brands. I really like Yamasa Kombu Tsuyu. But, the commercially available ones are expensive and may not be readily available outside of Japan. Normally the commercial brands fall into those which can be used straight ie no mixing with additional water or concentrated like this recipe. BTW, the (men) part means noodle in Japan, so mentsuyu means noodle broth and mendare means noodle sauce. But, this type of broth is the basis for many, many Japanese cooking and I hope you can make this and keep it bottled in the refrigerator. Once made, it is easily kept in the fridge for at least one year. This stock should go through several changes of cheesecloth to make sure it is completely clear of all debris before storing in the fridge. The leftover katsuobushi (bonito flakes) and kombu seaweed can be used for other things. I like to chop of kombu and stir fry it with katsuobushi, sesame seeds and a bit of teriyaki type sauce for making furikake which sometimes is used in plain rice in Japan or onigiri rice balls. This is my first one tsuyu recipe and I do have several versions of tsuyu and I plan to post additional ones in the future. The cup size I'm using is the Japanese cup size which is 200 ml = 1 Cup. When I mention soy sauce, I'm referring to the regular soy sauce and not light soy sauce which has more salt content and less color.