Bring a small pot of water to a boil and cook the egg for 6.5 minutes, then immediately transfer to an ice bath, peel, and slice in half.
Season the flank steak with sea salt and black pepper on both sides.
Heat a cast-iron skillet over medium-high heat with half of the sesame oil and sear the steak for 3-4 minutes per side until medium-rare, then remove from heat to rest.
In a medium saucepan, sauté the minced ginger and garlic in the remaining sesame oil until fragrant.
Pour in the beef bone broth and tamari, bringing the liquid to a gentle simmer over medium heat.
Add the brown rice ramen noodles and sliced shiitake mushrooms to the broth, cooking for 3-4 minutes until the noodles are tender.
Submerge the baby bok choy in the hot broth for the last 60 seconds of cooking until bright green and slightly wilted.
Slice the rested steak against the grain into thin strips.
Divide the broth, noodles, and vegetables into a large bowl, then top with the sliced steak, soft-boiled egg, and fresh scallions.