Tip the kimchi into a sieve over a liquid measuring cup, and press down to extract as much juice as possible, Measure the juice and, if need be, top it up to just under 1 cup with tap water. Roughly chop the drained kimchi.
In a large bowl, use a fork to whisk the flours and salt, then stir in the kimchi juice. Add the kimchi, tofu, bean sprouts and most of the green onions — saving a small handful of the onions for the sauce — and stir again. The batter should be wet but scoopable. Leave to stand for 10 minutes.
Meanwhile, make the dipping sauce. In a small bowl, mix the soy sauce, sesame oil, vinegar, chile flakes, the reserved green onions and the sesame seeds. Shred the spinach and put into a salad bowl. Add 2 tablespoons of the dipping sauce and toss to coat.
To cook the pancakes, heat ½ tablespoon of oil in a medium frying pan (ideally nonstick) on a medium flame and swirl it around to coat the base of the pan. Pour in a quarter of the batter (I used a ladle) and spread it out with the back of the spoon until it’s 6 inches in diameter.
Cook for 3 to 5 minutes, until the bottom is crisp and golden, then flip and cook on the other side until that, too, is crisp and golden. Transfer to a warm plate, cover with foil, and repeat with the remaining batter, adding a little extra oil to the pan for each pancake, if need be.
Serve warm with a big handful of spinach salad scattered on top and sprinkled with sesame seeds. Serve the sauce in little bowls on the side.