Boil water and cook soba noodles for 4-5 minutes until tender, then drain and rinse with cold water to prevent sticking.
In a small bowl, whisk together the gochujang, tamari, grated ginger, minced garlic, and water until the glaze is smooth.
Heat the sesame oil in a large skillet or wok over medium-high heat.
Season the diced chicken with sea salt and black pepper, then add to the skillet and cook until golden and cooked through, about 6 minutes.
Add the broccoli florets and sliced red bell pepper to the pan, stir-frying for 3-4 minutes until the vegetables are vibrant and tender-crisp.
Pour the gochujang sauce over the chicken and vegetables, stirring for 1 minute until the sauce becomes a glossy glaze.
Fold in the cooked soba noodles and toss gently until everything is well combined and heated through.
Serve immediately in a bowl, garnished with thinly sliced green onions and a sprinkle of sesame seeds.