If using, combine all ingredients for the dipping sauce in a small bowl and set aside.
In a large mixing bowl, stir together flour, potato starch, and baking powder.
In a separate bowl, stir together water and kimchi juice. Slowly add this to the flour mixture while whisking until smooth.
Add kimchi, onion, and green onion, and fold to combine. Add more water if the batter seems too thick - the batter should be like a thin pancake batter.
Add 1 tbsp of avocado oil in a skillet over medium high heat.
Scoop out some of the batter on the skillet and spread in a thin even layer (the amount of the batter will depend on the size of the pan - I was able to make 3 pancakes in a 9-inch skillet).
Cook for 3 minutes, until the edges are golden. Flip, add more oil to the sides, then tilt the pan so the oil can spread out through the bottom.
Press the pancake down with a spatula, then cook for another 3 minutes until crisp and brown on the bottom.
Remove from the pan, then repeat with the rest of the batter.
Slice into bite sized pieces and serve with the dipping sauce, if using.