For ichiban dashi, put kombu and 4 cups water into a small pot and heat over medium-high heat until water almost begins to boil. Transfer kombu to a small bowl; set aside to use for later if making niban dashi. 

Add 1/4 cup cold water to pot with kombu-infused water, then add bonito flakes. When water returns to a boil remove pot from heat and set aside to let stand for 1 minute. Strain contents of pot into a large bowl; reserve strained bonito flakes to make niban dashi, if you like. Serve ichiban dashi right away or use it as a base to make clear soups.

For Niban dashi, put reserved kombu, strained bonito flakes and 6 cups water into a medium pot and heat over medium-high heat until water almost begins to boil. Reduce heat to medium-low and simmer for 15 minutes. Add remaining 1 cup bonito flakes and remove pot from heat. Set aside to let stand for 1 minute, then strain contents of pot; discard solids. Serve niban dashi right away, or use it as a base for thick soups or sauce.