Slice the chicken breast into thin, bite-sized strips and season them with sea salt and black pepper.
In a medium pot over medium heat, add a splash of the chicken broth to sauté the minced garlic and grated ginger for 1 minute until fragrant.
Pour in the remaining chicken broth, tamari, and sriracha, bringing the liquid to a gentle simmer.
Add the chicken strips to the simmering broth and cook for 4-5 minutes until the chicken is opaque and cooked through.
Stir in the sliced mushrooms and baby bok choy, simmering for another 2 minutes until the greens are wilted but still bright.
Meanwhile, cook the soba noodles in a separate pot of boiling water according to package directions, then drain.
Divide the cooked noodles into a deep bowl and ladle the spicy chicken and vegetable broth over the top.
Garnish with thinly sliced green onions and an extra drizzle of sriracha if desired before serving hot.