01 -
Slice the beef sirloin thinly against the grain. Slice the yellow onion and bell peppers into strips. Chop the kimchi and set aside.
02 -
Combine low-sodium soy sauce, sesame oil, and, if desired, minced garlic and a pinch of sugar in a bowl. Add sliced beef and toss to coat. Let marinate for at least 15 minutes in the refrigerator.
03 -
Heat vegetable oil in a large skillet over medium-high heat. Add onions and bell peppers, sautéing until they are softened and slightly caramelized, about 5 minutes.
04 -
Push vegetables to one side of the skillet. Add the marinated beef to the empty side and cook, stirring occasionally, until browned and just cooked through, approximately 5 minutes.
05 -
Add chopped kimchi to the skillet. Stir everything together and cook for an additional 2 minutes until well combined.
06 -
Arrange toasted hoagie rolls on a baking tray. Distribute the bulgogi mixture evenly among the rolls, top each with a slice of provolone or American cheese, and broil for around 2 minutes until the cheese is melted and bubbling.