Place all ingredients for Korean BBQ Bulgogi Beef in a shallow bowl or plastic bag with zipper top. Place in refrigerator and marinate for at least 4 hours, up to overnight.
Fry Wonton Wrappers into Chips
Line a large plate with paper towels. Heat one inch of oil in a cast iron skillet over medium high heat, or to 350°F.
Fry a single, slightly overlapping is ok, layer of wonton wrappers until golden brown. Flip wonton wrappers to brown the other side. Transfer fried wonton chips to paper towel–lined plate. Sprinkle with salt while still hot. You will have to do this in about 5 or 6 batches.
Cook Beef and Corn
Heat 1 tablespoon oil in cast iron skillet over medium-high heat. Remove beef and onions from marinade, add to hot skillet, and cook until browned, about 8 minutes. Transfer cooked bulgogi beef to a plate and set aside. Discard any oil in the skillet.
If you are pan roasting/cooking the corn, pour off oil from the cast iron skillet, leaving just a shimmer on the surface. Turn heat to medium. Add corn to hot skillet and roast until corn starts to char. Remove corn to plate or bowl.
Assemble the Nachos
Turn on broiler in oven to high.
Wipe out the cast iron skillet with a paper towel. Begin building Korean BBQ Nachos starting with a layer of wonton chips in the bottom of the skillet.
Scatter half the cooked Korean BBQ Bulgogi Beef over the chips. Add half the corn, then half the shredded cheese. Repeat the layers one more time, ending with cheese.
Place the skillet with the Korean BBQ Nachos under the broiler until the cheese is melted and bubbly, about 3 minutes. Garnish with chopped kimchi, sliced avocado, sliced scallions, cilantro, and jalapeños. Serve extra toppings in bowls alongside.