01 - Set oven to 350°F (180°C) to preheat.
02 - Cook ramen noodles in boiling water for about 2 minutes less than package instructions. Drain and set aside.
03 - Heat vegetable oil in a large skillet over medium heat. Add chopped onion, minced garlic, and grated ginger; cook until fragrant and translucent, about 3 minutes.
04 - Add ground pork to skillet. Cook, breaking up the meat, until browned throughout.
05 - Stir in gochujang, crushed red pepper, crushed tomatoes, soy sauce, rice vinegar, sugar, salt, and pepper. Simmer for 10 minutes until slightly thickened.
06 - In a bowl, combine ricotta cheese, egg, half the shredded mozzarella, and half the grated parmesan. Stir until fully blended.
07 - Spread a thin layer of meat sauce on the bottom of a 9x13-inch (22x30 cm) baking dish. Place a layer of ramen noodles over the sauce.
08 - Spread one-third of the ricotta mixture over the noodles, followed by one-third of the meat sauce. Repeat layering noodles, cheese mixture, and meat sauce twice more. Finish with remaining meat sauce on top.
09 - Sprinkle remaining mozzarella and parmesan evenly over the surface.
10 - Cover with aluminum foil and bake for 20 minutes.
11 - Remove foil and bake for 10 to 15 minutes more, until the top is bubbling and lightly golden.
12 - Allow casserole to stand for 10 minutes before slicing. Garnish with sliced green onions if desired.