For the dressing: In a small bowl, combine the mirin, olive oil, soy sauce and vinegar and mix well.
For the salad: Cook the noodles according to the instructions on the packet. Drain and refresh under cold water, then add a few dashes of sesame oil to keep them from sticking and set aside.
Heat a wok over high heat and add the vegetable oil. Add the garlic and mushrooms and stir-fry until the mushrooms begin to soften, 1 to 2 minutes (adding a splash of water if necessary to facilitate cooking). Season with the light soy sauce and remove from the heat.
In a large serving bowl, add the noodles, mushrooms, sun-dried tomatoes and olives. Toss, and then pour the rice vinegar dressing over the salad. The dish is best kept refrigerated and served chilled.
When ready to serve, sprinkle with ground peanuts and arugula.