Soak the sweet potato vermicelli in water for about 15 minutes.
In a pot of boiling water, cook the spinach until it turns bright green, about 2 minutes. Drain the spinach and run it under cold water to stop the cooking. Squeeze out as much excess liquid as possible and set it aside.
In a very large skillet, heat 1 tablespoon of the olive oil over medium-high heat. Add the carrots and sauté until they start to turn soft, about 2 minutes. Season with salt and pepper. Remove the carrots and place in a large bowl. Repeat with the red bell pepper, the yellow bell pepper, and the green bell, followed by the red cabbage, seasoning each to taste with salt and pepper and adding to the bowl with the carrots. If necessary, add more oil to the pan as you go. The reason the vegetables are sautéed separately is to ensure that the flavors don’t muddle together.
In the same pan, heat the remaining 1 tablespoon olive oil over medium-high heat. Add the onion, garlic, mushrooms, and salt and pepper to taste and sauté until the mushrooms are browned, about 5 minutes. Add 1 tablespoon of the soy sauce and 1 tablespoon of the maple syrup to deglaze the pan.
Transfer the onions, mushrooms, and garlic to the large bowl of vegetables. Add the cooked spinach.
Bring a large pot of water to boil. Add the soaked vermicelli and cook them for 3 minutes. Add 1/2 cup cold water to the pot and when the water starts to boil again, add another 1/2 cup cold water. When the water comes to a boil, check the noodles to see if they are cooked (they should be tender and springy). If not, repeat.
Drain the cooked noodles and rinse them in very cold water. Shake off the excess water and add the noodles to the bowl of vegetables.
Add the remaining 2 tablespoons soy sauce and remaining 1 tablespoon maple syrup along with the sesame oil, a dash of black pepper, and the sesame seeds.
Mix using chopsticks or your hands. Taste and add additional soy sauce, maple syrup (I like mine sweet!), or black pepper if desired.