Season the beef slices with soy sauce, sesame oil, garlic, and a pinch of salt. Let it rest for 15 minutes.
Heat a grill pan and cook the beef quickly until charred on the edges but still juicy inside. Set aside.
Cook the ramen noodles according to package directions, then drain and keep warm.
In a pan, melt butter and stir in gochujang, chili flakes, and garlic. Cook until fragrant.
Pour in the heavy cream and whisk until smooth. Let it simmer gently until slightly thickened.
Toss the cooked noodles in the sauce until well coated.
Serve noodles in bowls, top with grilled beef, sliced green onions, and sesame seeds.