Start by slicing the beef into thin strips, about ¼ inch thick. In a mixing bowl, combine soy sauce, gochujang, sesame oil, brown sugar, minced garlic, and black pepper. Coat the beef strips thoroughly in this marinade, cover, and let them marinate in the refrigerator for at least 30 minutes.

While the beef marinates, whisk together the mayonnaise, sriracha, sesame oil, garlic powder, and sugar in a small bowl until smooth. Transfer to the refrigerator.

In a large pot, bring 4 cups of water or broth to a gentle simmer. Add gochugaru, soy sauce, rice vinegar, sesame oil, and salt, stirring well. Introduce the ramen noodles, cooking for about 3 minutes until al dente.

Preheat a grill pan over medium-high heat. Sear the beef for 2-3 minutes on each side until caramelized. Let the beef rest for a few minutes before slicing.

In large serving bowls, divide the cooked ramen and broth. Top with grilled beef slices, drizzle over the creamy sauce, and garnish with green onions and sesame seeds.