Cook the soba noodles in boiling water according to package directions, then drain and set aside.
In a small bowl, whisk together the gochujang, tamari, rice vinegar, and sesame oil to create the glaze.
Season the diced chicken breast evenly with the sea salt and black pepper.
Heat a large non-stick skillet over medium-high heat and sear the chicken until it is golden brown and cooked through.
Add the minced garlic, grated ginger, and broccoli florets to the skillet, sautéing for three minutes until the broccoli is tender-crisp.
Pour the gochujang sauce over the chicken and vegetables, tossing constantly until the sauce becomes thick and glossy.
Divide the cooked soba noodles into a bowl and top with the spicy chicken stir-fry.
Garnish the dish with thinly sliced green onions before serving.