Whisk together all ingredients for the Sauce in a medium bowl (except for garnishes) and set aside.

Cook spaghetti in large pot of salted boiling water to al dente, according to package instructions. Drain and rinse in cold water. Transfer drained noodles into large serving bowl. Sprinkle 2 TB sesame oil onto cold noodles and toss to coat.

Add cucumber, garlic, carrots, scallions, and shredded chicken to the noodles. Toss well.

Whisk sauce again and pour over noodle mixture; toss well to ensure even coating.

Divide into serving plates and serve at room temp. Garnish with toasted sesame seeds and/or chopped peanuts if desired.