Bring a small pot of water to a boil and cook the egg for exactly 6.5 minutes before transferring to an ice bath to peel.
Season the chicken breast with sea salt and black pepper, then sear in a skillet until the exterior is golden-brown and the center is cooked through.
In a medium saucepan, combine the chicken bone broth, tamari, minced ginger, and minced garlic, bringing the liquid to a gentle simmer.
Add the shiitake mushrooms and bok choy to the broth, poaching them for 3 minutes until the greens are vibrant and tender.
Cook the soba noodles in boiling water according to the package instructions, then drain and place them into a deep serving bowl.
Slice the seared chicken and the soft-boiled egg, arranging them neatly over the noodles.
Pour the aromatic broth and vegetables over the bowl, finishing with a drizzle of toasted sesame oil and a garnish of sliced green onions.