Cook noodles: Cook noodles in a large pot of boiling water according to package directions. Drain and rinse under cool running water. Lighlty drizzle with neutrel oil and toss to prevent the noodles from sticking together; set aside. Cook mushrooms: Heat 3 tablespoons neutral oil in a large cast iron skillet over medium-high heat. Once hot, add the mushrooms, stir to coat and spread into an even layer (some will overlap which is okay). Cook undisturbed until they turn deeply golden brown on the bottom, about 10 minutes. Meanwhile... Make stir fry sauce: Meanwhile, whisk the Stir Fry Sauce ingredients together in a medium bowl; set aside. Caramelize mushrooms: Once the bottoms of the mushrooms are golden, give them a stir and continue to cook, stirring occasionally, until the mushrooms are deeply caramelized, about 5 more minutes.
Stir fry vegetables: Add the bell peppers, carrots, ginger, garlic and white parts of green onions to the mushrooms and cook an additional 2 minutes, or until the onions are softened. Combine: Add the Sauce and bring to a simmer until slightly thickened, about 1 minute. Add the noodles, spinach, and basil and toss until the spinach is wilted, about 1 minute.
Garnish: Garnish with desired amount of green onions and sesame seeds.