In a small bowl, whisk together the sesame oil, brown sugar, garlic, ginger, and rice vinegar.
Prepare the veggies:
Soak the shiitake mushrooms in hot water for 10-15 minutes or until softened. Drain and slice thinly. Julienne the carrots using a vegetable peeler or mandoline. Wash and chop the spinach into bite-sized pieces. Thinly slice the red onion. Cut the green onions into small pieces.
Heat a large skillet or wok over medium-high heat. Add a drizzle of sesame oil.
Add the shiitake mushrooms and carrots to the pan and stir-fry for 2-3 minutes or until softened.
Add the spinach, red onion, and green onions and stir-fry for 1-2 minutes or until wilted.
Remove the veggies from the pan and set aside.
Prepare the Noodles:
Cook the glass noodles according to the package directions. Drain and rinse thoroughly.
Assemble:
In a large bowl, combine the cooked glass noodles, sauce, cooked veggies, and sesame seeds.