Place a pot of water on the stove for the soba and bring to a boil.
For the sauce: Place the stock, tamari, mirin, sherry, sugar, Worcestershire, ginger and garlic in small pot. Bring to a rolling boil and reduce by half, 15 to 20 minutes over medium heat. Reduce the heat to a low boil or rolling simmer.
For the chicken: Add the oil to a skillet and heat over high heat. Sprinkle the chicken with lightly with salt and more aggressively with pepper. Cook 8 to 9 minutes, turning occasionally, then remove from the heat. Raise the heat again to high. Add the peppers and stir for a few minutes, but keep them tender-crisp. Add the scallions and garlic and toss 1 minute, then remove from the heat.
Cook the soba according to package instructions, a couple of minutes, to al dente. Drain.
Place a quarter of the soba noodles in shallow bowls or on plates. Top with a few peppers and scallions. Slice 1 chicken breast per portion and fan on top of the soba. Pour the sauce evenly over the dishes and serve.
Recipe courtesy of Rachael Ray