Cultures around the world are renowned for their famous fermentables — fish sauce, kimchi, sauerkraut, yogurt and beer, to name a few. Natto, Japanese fermented soybeans, are a dietary staple (with a fairly steep learning curve for foreign palates). And funazushi takes it one step further. What is funazushi? It’s the funkiest sushi you’ve ever eaten.

While sushi can be made from nearly any fresh, edible fish — seriously, try sardine sushi — funazushi is traditionally made with a kind of Japanese goldfish called nigorobuna, unique to Lake Biwa in Shiga Prefecture. Originally a food preservation method to fortify rice farmers’ food stores through the rainy season, the fish is pickled in salt to draw out moisture, then compressed with steamed rice to seal out air and encourage fermentation. The resulting product, harvested several months later, evokes strong, tangy blue cheese, feet and perhaps a whiff of ammonia. Like the more common fermented fish preparation kusaya, which translates to “smells bad,” funazushi is enjoyed as a delicacy around Japan. Watch it prepared in the video below, check out these other next-level pieces of sushi, and brush up on your advanced Japanese cuisine knowledge before your next trip to the sushi bar.