Renowned chef Nobu Matsuhisa prepares miso soup using homemade dashi, a Japanese stock made from just two ingredients and water: kombu, or giant kelp, and katsuobushi, better known as bonito flakes.
Wipe kombu lightly with a dry cloth. Place in a large pot with 2 quarts cold water. Bring to boil over medium heat. Remove kombu.
Return stock to a boil. Add bonito flakes, and remove from heat. Let stand 2 to 3 minutes. Strain through cheesecloth to remove flakes.