Marinate the Beef: In a large bowl, whisk together soy sauce, dark brown sugar, mirin, minced garlic, mashed kiwi, diced onion, sesame oil, and black pepper until well combined. Add thinly sliced ribeye or flank steak, ensuring every piece is coated. Cover and refrigerate for at least 1 hour, preferably overnight.

Cook Bulogi: Heat a tablespoon of oil in a large skillet over medium-high heat. Once shimmering, add the marinated beef, cooking for approximately 4–5 minutes. Stir occasionally until beef is about 80% done. Remove from heat and drain any excess liquid.

Preheat Oven: Preheat your oven to 500°F (260°C). This high temperature is essential for achieving that perfect, bubbly cheese topping.

Assemble Nachos: On a parchment-lined baking sheet, spread a layer of tortilla chips. Generously sprinkle mozzarella over the chips, then distribute cooked bulgogi evenly across the cheese. Drizzle Sriracha, Japanese mayo, and unagi sauce over the top.

Bake: Place the assembled nachos in the preheated oven. Bake for 5–10 minutes until cheese is melted and bubbly with a slight golden hue.

Add Fresh Toppings: Once the nachos are out of the oven, top with well-drained kimchi, chopped green onions, and a sprinkle of sesame seeds.

Cool Briefly: Allow nachos to cool for a few minutes on the baking sheet before cutting into portions for serving.