Prep the Steak: Place the ribeye steak in the freezer for 30 minutes to make it easier to slice. Once chilled, slice it into thin strips about 2mm thick.
Marinate the Meat: In a mixing bowl, combine the soy sauce, gochujang, minced ginger, brown sugar, rice wine, minced garlic, black pepper, grated apple, and sesame oil. Add the steak, coat well, and let it marinate for at least 30 minutes at room temperature.
Cook the Steak: Heat oil in a large frying pan over high heat. Add the marinated steak and cook for 4-5 minutes undisturbed to build caramelized edges. Drain off any excess liquid as it cooks. Remove the steak from the pan and let it rest.
Sauté the Veggies: In the same pan, add the sliced bell peppers and cook for 2-3 minutes until slightly softened but still crunchy.
Prep the Bread: Brush melted butter onto one side of each slice of bread. Lay the bottom slices butter-side-down on the counter.
Assemble: Layer the cooked peppers, rested steak, mature cheddar, red onion, jalapeños, and scallions on the bread. Top with the remaining bread slices, butter-side-up.
Toast: Toast the assembled sandwiches in the pan over medium-low heat for 2-3 minutes per side. Press down gently with a spatula until golden brown and the cheese is melted.
Sauce and Serve: Mix mayonnaise with minced garlic to create a garlic mayo. Open the toasted sandwiches, drizzle with the garlic mayo and sweet chili sauce, close back up, and serve immediately.