Dashi

• 1 (4-inch) square kombu
• 1½ cups bonito flakes

Rinse the kombu in cold water to remove dust. Put the kombu in a pot with 2½ quarts cold water. Bring to a boil. Remove from the heat and add the bonito flakes. Let steep for 15 minutes, then pour through a fine-mesh sieve lined with a clean kitchen towel or cheesecloth.