In a large pot, bring beef broth to a boil. Add soy sauce, mirin, ginger, and garlic. Reduce heat and simmer for 30 minutes to develop the broth's flavor.

Add ramen noodles to the simmering broth and cook according to package directions (usually 3-5 minutes).

While noodles are cooking, quickly sear the thinly sliced beef in a separate pan with sesame oil until browned. Be careful not to overcook.

Divide the noodles and broth among bowls. Top with seared beef, chopped scallions, and nori strips. Serve immediately.