Mung beans may not be a familiar ingredient to many cooks here, but these legumes are popular throughout much of Asia, and are becoming easier to find here. They can range in color from green to yellow to black, taste a little sugary, and are sold whole, split, or hulled. Opt for the hulled variety, which means you can skip the soak.
In India, they are commonly used in curries like moong dal. Here, they are utilized in a popular and traditional Korean dish, often served at Seollal, the Lunar New Year. — Will Budiaman
*Note: Kimchi is often sold in large bags or jars. Here, “kimchi juice” simply refers to the pickling liquid leftover, so make sure to reserve some for use.
**Note: If you have purchased mung beans that are not hulled, soak in cold water overnight (or about 2 hours in warm water) and rub between your hands to hull. Repeat as necessary to get clean hulled mung beans and drain completely. (If you skip this process, you will end up with green pancakes!)
***Note: Dried bracken ferns are sold as gosari at Korean or Asian supermarkets all year round. They should be soaked in water for several hours until soft and rinsed well. Rinsing is really important because if you skip this step then your pancake will have a distinctive fern smell.
If you are using fresh fern, I would recommend lightly sautéeing it with some canola oil rather than boiling — about 3 minutes over medium-high heat, lightly seasoned with salt and cooled before adding to the mix.
In the bowl of a food processor, combine the kimchi juice, 1/3 cup of the water, garlic, and beans and process until it resembles coarse cornmeal, about 30 seconds (your pancakes will have better texture if you don’t blend too much).
Transfer the blended beans to a large bowl and add the sprouts, kimchi, ferns, scallions, fish sauce, sesame oil, salt, and pepper. Mix well.
Heat the canola oil in a large skillet over medium heat. Add about ⅓ cup of the batter and cook about 2 minutes on each side until golden brown. Meanwhile, in a bowl, combine the soy sauce, vinegar, and remaining water to make the dipping sauce. Serve the pancakes warm with soy dipping sauce.