Cook noodles according to package directions. Drain well and return to pot. Cover and set aside away from heat.
Meanwhile, in a small bowl, whisk broth, arrowroot, tamari and sesame oil. Set aside.
In a wok or large skillet, heat safflower oil on medium-high. Add garlic, ginger and onion and stir-fry, stirring constantly, until fragrant but not brown, about 1 minute. Add bell peppers and mushrooms and stir-fry until tender-crisp, about 2 minutes. Add scallops and stir-fry until just opaque, about 2 more minutes. Add broth mixture, spinach and edamame and stir-fry until sauce thickens and spinach wilts, about 2 minutes. Add noodles and stir to combine. Serve immediately.
Serving Size: 2 oz soba, 4 oz scallops, 1 cup pepper-edamame mixture