Thinly slice your steak, then add to a bowl along with soy sauce, sesame oil, honey, apple, garlic, and black pepper. Leave to marinate for at least 30 minutes.
Whisk together the gochujang, soy sauce, sesame oil, rice vinegar, and honey. Set aside.
Add a splash of oil to a skillet and heat on high. Add the steak and quickly sear until cooked through and nicely browned. Remove from the pan.
Add another splash of oil, then your sliced onion, peppers, spring onions, and garlic. Cook until softened.
Meanwhile, cook your rigatoni. Add the cabbage and enoki mushrooms. Pour sauce over the softened vegetables, then add the steak.
Toss to coat, then add a ladle of starchy pasta water. Allow to cook for a few minutes.
Add a sprinkle of mozzarella cheese, stir through, then add your pasta. Ensure everything is well coated, then add another layer of cheese. Finish under the grill until golden and bubbly, then garnish with sliced spring onions, sesame seeds, and gochugaru.