Season the chicken breast evenly with sea salt and black pepper.
Heat the sesame oil in a medium pot over medium-high heat and sear the chicken until golden and cooked through.
Remove the chicken from the pot, let it rest for 5 minutes, then slice it into thin, bite-sized strips.
In the same pot, add the minced garlic, grated ginger, and sliced shiitake mushrooms, sautéing for 2 minutes until fragrant.
Pour in the chicken broth, tamari, and sriracha, then bring the liquid to a gentle boil.
Add the brown rice ramen noodles to the boiling broth and cook according to package directions, typically 3 to 4 minutes.
Stir in the chopped bok choy during the final minute of cooking until the leaves are wilted and the stems are tender-crisp.
Ladle the soup and noodles into a large bowl, top with the sliced chicken strips, and garnish with fresh green onions.