Whisk the all-purpose flour, rice flour, cold water, egg, and salt together in a bowl until just combined. Don't overwork it — a few small lumps are fine, and overmixing develops gluten that makes the pancake chewy instead of crisp.

Rest the batter in the fridge for at least 10 minutes. Cold batter hitting a hot pan is what creates the crisp edge; room-temperature batter steams instead of frying.

Lay the scallions in the pan first in a flat, even layer roughly the size of the finished pancake, rather than stirring them into the batter.

Heat 2 tablespoons of oil in a nonstick or well-seasoned pan over medium heat until it shimmers. Ladle the batter evenly over the scallions, covering them completely.

Scatter the seafood over the top while the batter is still wet, pressing each piece down gently so it's held in place once the batter sets.

Cook undisturbed for 4 to 5 minutes, until the underside is deep golden and the edges have visibly crisped and pulled slightly away from the pan.

Add the remaining 1 tablespoon of oil around the edges, then flip using a large plate or a second pan — slide the pancake onto the plate, then invert the pan over it and flip both together.

Cook the second side another 3 to 4 minutes, pressing down once with a spatula halfway through to flatten it against the hot pan for even crisping.

Slide onto a cutting board, let it sit 1 minute before slicing into wedges — cutting immediately releases steam that softens the crust. Serve with the dipping sauce made from soy sauce, rice vinegar, gochugaru, and sesame seeds.