Dashi is a Japanese stock or broth, and it is a fundamental ingredient in many Japanese dishes. Dashi powder is the dried version. It can be made from kombu (dried kelp), katsuo-bushi (dried bonito flakes), niboshi (dried small sardines), hoshi-shiitake (dried shiitake mushrooms), and more. Dashi creates a savory umami flavor from all these ingredients.
The cheaper brands will have MSG, and will do in a pinch. Look for the ones with no MSG as the taste and quality will be better.
Where to Buy
Most Asian markets will carry at least one brand, usually with MSG. Japanese grocery stores will more likely carry more brands and have a choice with no MSG.
Buy at Amazon and support this site: Maruhachi Katsuo Kombu Awase Dashi (no MSG), 8.81 Ounce Unit