Mix the flour, boiling water, and sesame oil in a bowl.
Turn dough onto work surface and knead for several minutes.
Let dough rest for a few minutes while you chop scallions.
Roll the dough into a flat circle.
Drizzle with some sesame oil and sprinkle with scallions.
Roll into a cylinder, then cut into 8 pieces.
Press down on each piece, rolling into a circle.
Heat a nonstick pan over medium-high heat.
Add some grapeseed oil, and cook pancakes until golden brown on both sides.
To prepare the bulgogi: Slice steak thinly against the grain, and season with salt and pepper.
Combine the rest of ingredients in a food processor.
Marinate steak in this mixture for 1-2 hours.
Add steak and some of the marinade to a pan and cook until liquid evaporates.
To assemble quesadilla: Top one scallion pancake with a layer of cheese, then a layer of bulgogi and then more cheese.
Cover with another scallion pancake.
Heat oil in a pan over medium-high heat.
Fry pancake, flipping once, until cheese is melted, about 2-3 minutes per side.
Top with kimchi.
Repeat with remaining ingredients.
Chef's note: because the scallion pancake are rustic in shape and size you may to trim the edges to get two to fit together nicely.
The scraps make a delicious snack while cooking.