Whisk together the flour, starch and salt. Stir in the onion and chili.
Stir in the kimchi until well incorporated. Start adding water (you can also use kimchi juice if you have enough). You want to add enough water that you have a good batter that's not too thick, but not soupy either. I normally find between 2/3 cup and 3/4 is just right.
Heat a cast iron skillet over medium high heat. Add the oil and swirl to coat the bottom of the pan. Pour in the kimchi batter and use a spatula to spread it to the edges of the pan in an even layer.
Let the pancake cook for 4 - 6 minutes on one side, or until starting to brown. Flip it over and finish cooking the other side until browned. Remove from heat and serve with your favorite dipping sauce!