- 1 (4 inch) piece dashi kombu (dried kelp)
- 4 cups water
- Wipe the kombu with a damp cloth to clean it. Cut into 1-inch pieces and place into a saucepan along with the water. Bring to a boil; reduce heat to medium-low and simmer 20 minutes. Remove from the heat and let stand a few minutes. Strain through a mesh strainer before using.