Fresh mepssalgaru is sold at rice cake shops or mill shops in Korea, but in the United States you can buy it frozen in Korean grocery stores. There are glutinous rice cake flours that differ from mepssalgaru, so make sure to ask someone specifically for mepssalgaru. Thaw frozen mepssalgaru slightly at room temperature (at least 30 minutes) and sift for the songpyeon. After 30 minutes, the flour will still have big, hardened chunks, so crush all the flour with hands or metal spoons before sifting it. Store leftover mepssalgaru in the freezer. Do not let it sit out at room temperature too long or it will lose moisture. Gardenia fruit tea and mugwort powder are available at Korean grocery stores and online.