Cook the noodles: Blanch udon noodles in boiling water for about 1 to 2 minutes or if using dry noodles cook according to package instructions. Drain well and immediately rinse with cold water. Set aside.
Make the sauce: Add all the sauce ingredients together to a bowl and whisk until combined.
Saute the sauteables: Heat the olive oil in a large skillet or a wok. Add the chicken pieces and cook until chicken is no longer pink and starts to brown slightly. Add the mushrooms and cook for a couple more minutes until mushroom are starting to brown.
Finish the dish: Add the udon noodles and prepared sauce to the wok, toss everything together well and cook until the noodles are heated through. Garnish with green onions and serve hot.
These noodles will keep for 3 – 4 days in the fridge if stored in an airtight container. I wouldn’t recommend freezing this dish as the noodles don’t thaw well after time in the freezer.