Bring a medium pot of water to a boil for the noodles.
Heat a large skillet over medium-high heat and add the ground turkey, cooking until browned while breaking it into small crumbles.
Add the minced garlic, grated ginger, Chinese five spice, sea salt, and black pepper to the turkey and sauté for 2 minutes until fragrant.
In a small bowl, whisk together the tahini, tamari, chili oil, and rice vinegar with 2 tablespoons of warm water until the sauce is smooth and creamy.
Cook the soba noodles in the boiling water according to package directions, adding the chopped bok choy to the pot for the final 60 seconds of cooking.
Drain the noodles and bok choy thoroughly, then transfer them into the skillet with the turkey.
Pour the tahini sauce over the noodle mixture and toss everything together over low heat until well-combined and heated through.
Garnish with thinly sliced green onions and serve immediately.