Place vermicelli in large bowl, pour boiling water over the noodles and let it soften, about 6-8 minutes, or until softened and chewy. Drain and rinse under cold water. Using scissors, cut the noodles into shorter lengths, about 8 inches. Toss with 1 teaspoon sesame oil and set aside.
In a smal bowl, mix soy sauce, sugar, and sesame oil together until sugar dissolves. Set aside.
Steam the spinach in a steamer for about 1-2 minutes (or blanch the for 30 seconds). Remove immediately and rinse in cold water. Drain and gently squeeze out all the water from spinach. Form into a ball, then using scissors, cut it in half. Combine spinach with 1 teaspoon of sesame oil and pinch of salt. Set aside.
Heat 1 teaspoon canola oil in a large skillet over medium high heat. Add onion and a pinch of salt. Stir-fry for about 2 minutes, or until onion is slightly translucent. Remove from pan.
In the same skillet, repeat the whole process with carrots and mushrooms.
In a large mixing bowl, add the noodles and all the vegetables. Pour in the soy sauce mixture. Using your hands toss until all the ingredients are coated evenly with the sauce. Taste and season with salt, if needed. Add the toasted sesame seeds and a drizzle of sesame oil. Serve immediately.