Combine the flours and about 200ml (7fl oz) cold water, adding water a little at a time and mixing until the mixture is the consistency of thin pancake batter. Add the spring onions and black pepper and mix.
In a large frying pan or on a griddle, add just enough vegetable oil to thinly cover the surface, about 1 tablespoon at a time. Turn the heat to medium high. Add half the batter onto the frying pan in a large flat circle. Cook on one side until golden brown. Flip and cook the other side. Lower the heat as necessary to prevent burning, adding more oil as needed. Remove the pancake. Pour on the remaining batter and repeat.
Cut the pancake into 4 or 8 pieces. Serve hot with soy sauce or vinegar soy.
The secret to making any jun (panckaes) crispy is to use very cold water in the batter. Rice flour gives it a slightly chewier, stickier texture. If you can’t find rice flour, you can use all-purpose flour instead.
Recipe from Eating Korean: From Barbecue To Kimchi, Recipes From My Home, by Cecilia Hae-Jin Lee, published by John Wiley & Sons.