To make ahead: Refrigerate for up to 5 days or freeze for up to 3 months.
Tips: Kombu, or dried kelp, is mildly salty and slightly sweet. The strips often come covered with naturally occurring salts: don't wipe this off before cooking because it adds to the umami of the kombu. Find it in natural-foods stores.
Use dashi in Japanese Shiitake & Vegetable Rice (Takikomi Gohan), add dashi to steaming liquid for clams, or use in shrimp & grits: Simmer shrimp shells in dashi for about 10 minutes. Strain, then use the stock to cook the grits. Serve the grits topped with shrimp sautéed in garlic and sesame oil.