Preparation Put the water, dashima, shiitake mushrooms, and anchovies in a covered stockpot or other large pot and let stand at room temperature overnight, or for 8 to 12 hours. Remove the lid, set the pot over high heat, and heat until the surface of the water begins to ripple; pay attention, and do not let it come to a boil. Lower the heat to maintain a very gentle simmer (the ideal temperature is a few degrees below a light boil) and simmer for 80 to 90 minutes. Taste the dashi every 20 minutes to monitor the changes in flavor and texture. You will notice the texture becoming softer. I describe it as having a slippery, slightly viscous texture compared to tap water. The sea flavor will become stronger, and the dashi will become darker, like pale Earl Grey tea. The sweetness will take a while to appear, but when it does, the dashi is almost ready. When you can taste the sweetness and deep sea flavors, and the dashi has a very soft texture, it is done. Be vigilant, because dashi will become bitter if cooked too long. Strain the dashi into a covered container and store in the refrigerator for up to 2 days. After 24 hours, the dashi will begin to lose some of its flavor and it will turn slightly flat. Cooks' Notes It’s best to use dashi the same day you make it, though if you keep it refrigerated, you can use it for another day or two. By the third day, it will no longer taste fresh. Vegetarians can make a dashi from just dashima and dried shiitakes. Reprinted with permission from My Korea: Traditional Flavors, Modern Recipes by Hooni Kim, copyright © 2020. Published by W. W. Norton & Company.Buy the full book from Amazon.