Shichimi-togarashi or cayenne, optional - see notes
Gently pound the chicken tenderloins between 2 sheets of plastic wrap to flatten. Lightly season on both sides with salt and pepper and set aside.
Bring a large pot of very lightly salted water to a boil. Cook the soba noodles until tender, 4 to 5 minutes. Drain, rinse with cool water, drain again and set aside.
Heat the vegetable oil and 1 tablespoon of the sesame oil over medium-high heat in a large skillet or wok. Add the chicken and stir-fry until cooked through, 2 minutes per side. Using tongs, transfer to a cutting board and allow to cool.
Add the remaining tablespoon of sesame oil to the pan, then add the garlic. Stir-fry for 1/2 minute, then add the cabbage. Continue cooking until the cabbage is softened, then add the shiitake mushrooms. Stir-fry for 3 minutes longer, add the scallions, combine well and remove from the heat.
Slice the chicken tenderloins diagonally into 1/4-inch pieces and add to the cabbage mixture.
In a small bowl, combine the soy sauce, rice vinegar, sugar and mirin (see notes for substitution). Stir until the sugar is dissolved then add to the soba noodles and toss. Add the noodles to the chicken mixture and combine well.
To serve, plate individual servings and sprinkle with sesame seeds and a pinch of Shichimi-togarashi (or cayenne) if desired.
Tips for Making This Recipe
Mirin is a low-alcohol rice wine frequently used to lend a subtle sweetness to sauces and glazes in Japanese cuisine. It's available on the ethnic foods aisle of most supermarkets. Substitute with 2 tablespoons of sherry and an additional 1/2 teaspoon of sugar.
Shichimi-togarashi is a unique spice blend from Japan. The ingredients can vary a little, but generally it is made with togarashi (hot chili) powder, sesame seeds, dried tangerine peel, nori (seaweed), ground ginger and Szechuan pepper. You can find it online or in Asian markets. Substitute a pinch of cayenne if desired.