If you make fresh dashi stock frequently, you’ll find yourself with quite a bit of leftover kelp. Save the pieces in a plastic bag in the refrigerator for up to 10 days, and when you have about 48 square inches, make up a batch of these pleasantly spicy squares. Once prepared according to the recipe below, the kelp will keep, covered and refrigerated, for a month or more. A few squares will perk up a steaming bowl of plain white rice and add nutrition (particularly calcium) to your m