Put the uncooked glass noodles in a large bowl, cover them with boiling water, and let them sit for 4–6 minutes until soft and transparent. Then drain, rinse with cold water, drain again, and cut the noodles into 6–8 inch strands using kitchen scissors. Set aside.
Whisk together the toasted sesame oil, soy sauce, sugar, minced garlic, black pepper, and rice vinegar in a small bowl. Set aside.
Heat 1 teaspoon of vegetable oil in a wok or large pan over medium-high heat. Add the onion and red bell pepper, and stir fry for 1–2 minutes until slightly softened. Then transfer to a large mixing bowl.
Add more oil to the pan if needed. Then add the cabbage and carrots, and stir fry for 1–2 minutes. Transfer to the mixing bowl with the other veggies.
Add the mushrooms and garlic with 3 tablespoons of the sauce to the pan and cook for about 2 minutes. Then add the baby corn and the white parts of the scallions, and cook for another minute. Now, transfer to the bowl with other vegetables.
Put the remaining sauce and cut noodles in the wok. Then toss to coat and cook for 2–3 minutes until warm. Add the cooked veggies back to the pan with the noodles and toss to combine You can also put the noodle in the large bowl and toss.
Sprinkle the sesame seeds over the noodles and toss again. Now, taste the dish and add more soy sauce or salt if needed.
To serve, top with sliced green onions and sriracha, if desired. You can serve this dish hot or cold. It's really good topped with baked extra firm tofu or crispy fried tofu.