It’s Japanese or Korean, it’s green, but it’s not made out of seaweed. What is it?
Well, it’s probably flavored with the Asian version of mugwort. You often see red bean mochi and red bean buns flavored with mugwort, especially in the springtime. (Hence those boxes with white, green, and pink mochi.) Green mugwort mochi with red bean filling are called “yomogi mochi.” There’s also a kind without filling that is called “kusa mochi,” aka “weed mochi” or “grass mochi.” (In Korean food, mugwort is called “ssuk.”) The taste is not strong or bitter, at least in the mugwort foods I’ve had; it actually puzzles you to figure out what’s different. Possibly some cooks make the flavor stronger.
Here’s a post about making microwave yomogi mochi and kusa mochi, with fresh leaves. She gets the brighter green color with food coloring. This post has a lot of helpful explanations!
Here’s a video of a Japanese lady making it from the leaves. The baking soda in the water helps preserve the brighter green color. Joshin-ko is ordinary rice flour, and shiratama-ko is rice flour made from “glutinous” or sweet rice (which actually has no gluten but is sticky as heck). The benefit is that it is more elastic than mochi-ko (which is a different kind of rice flour made from the same sweet rice). However, before refrigeration it could only be made in the cold months, so shiratama-ko might be used here for historical reasons, because this kind of mochi is a springtime delicacy.
Here’s a video of traditional confectioners in Nara making yomogi mochi from scratch, ie, pounding the hot mochi with mallets in a big wooden tub. (Just like sumo wrestlers do for exercise, or like the Rabbit in the Moon!) Really really really from scratch, down on the Japanese farm. Also includes toasted mochi, and sweet red bean soup with sweet mochi dumplings. Mmmmmm. Red bean dessert soup…..
Mugwort (aka artemisia, from its plant family) is related to wormwood, but it’s got a lot less of the aromatics and of the potential toxicity. Translation: although you should probably go easy on the mugwort-flavor if you’re pregnant or breastfeeding, you’d have to eat a lot for it to hurt your baby and sometimes it’s been used to help. Still, better safe than sorry.)
Mugwort pretty much is a tasty weed. It has roots called “stolons” that go deep underground, so it’s hard to get rid of. You might as well eat it before it eats your yard. The other bad news is that a lot of people in Asia or Europe are allergic to its pollen (which is as bad as ragweed, though luckily the pollen doesn’t travel far from the original plant).
In Europe, dried mugwort leaves and flowers together were often used as a beer flavoring agent before hops got popular. It is still used occasionally by homebrewers. Its smell and presence was seen as protective and refreshing, and it was often gathered on St. John’s Eve for extra holy oomph. You can make tea out of it, and some people use it as a tonic or for various other stuff. The smell gives some people vivid dreams. (But it’s a diuretic like a lot of herbs, so go easy.) It apparently goes well with poultry. Sheep, poultry, and turkeys are said to fatten up well from eating mugwort.
My feeling is that it probably isn’t any kind of undiscovered super medicine. But it is a green herb with vitamins and aromatics that probably do make some people feel better. (Plus it’s slightly bitter if you eat it without sugar, and some people think a medicine should be bitter in able to work.) Don’t pay too much for this stuff; if you really want it you can grow it. Also, many Asian groceries carry “mugwort powder” or “artemisia powder,” which is just dried and powdered mugwort to be used as a spice and coloring agent. Apparently it is more concentrated than fresh leaves. Mugwort is also available in some US stores in pills as a dietary supplement (geez, does everything have to be a pill?).
Extra info: Korean myth has it that the god Hwanung once turned a bear into a woman by giving her nothing to eat but twenty cloves of garlic and a bundle of mugwort, and having her stay out of the sunlight for one hundred days. (Voluntarily. This was a talking-animal bear.) After she turned into a human and was sad about having no mate to give her human children, Hwanung married the ex-bear. Their son was Dangun, who became the founder of the first Korean kingdom, Joseon aka Gojoseon.
(Insert Arthur/Artos bear reference here.)