In a mixing bowl, combine the soy sauce, gochujang, sesame oil, brown sugar, minced garlic, and black pepper. Add the sliced beef, making sure it’s fully coated, and let it marinate for at least 30 minutes or overnight for deeper flavor.
In a separate small bowl, whisk together all the ingredients for the creamy sauce until well blended and smooth. Refrigerate until you're ready to serve.
In a saucepan, bring the broth to a gentle simmer. Stir in gochugaru, soy sauce, rice vinegar, sesame oil, and a pinch of salt. Add the ramen noodles and cook until just al dente, about 3 minutes. Take off the heat and set aside.
Heat a grill pan or skillet over high heat. Sear the marinated beef for 2 to 3 minutes on each side until it’s nicely caramelized. Let the meat rest briefly, then slice thinly against the grain.
To assemble, place the cooked noodles into serving bowls, pour over the seasoned broth, and drizzle with the creamy sauce. Top with the grilled beef, chopped green onions, toasted sesame seeds, and a dash of extra chili oil or gochugaru for added heat, if desired.