How to Make It
Pour 2 quarts water into a medium saucepan, and add kombu. Let stand until kombu doubles in size, about 30 minutes. Cook over medium-low until water is steaming and tiny bubbles collect on surface of kombu. Adjust heat to maintain water temperature below a simmer, and let steep for 30 minutes. Remove from heat, and add katsuobushi. Allow katsuobushi to settle at the bottom of the pot, about 2 minutes. Pour liquid through a fine wire-mesh strainer into a bowl. Discard solids.