Combine the Bragg's liquid aminos, sweetener and sesame oil in a medium sized bowl, and set aside.
Bring the water to a boil in a large pot. Add noodles, stir, and cook until tender, for about 5 minutes. Alternatively, you can bring water to boil, add noodles and remove from heat, and allow to sit for about 20 minutes or until tender.
Drain the water from the pot, using a colander to assist. Rinse the noodles with cold water, and drizzle with a little sesame oil. Mix the noodles so they can be coated with the oil to prevent sticking, and set aside.
Heat oil in a large skillet on medium-high heat. Add onion and garlic, and cook for about 3 minutes until onions are soft. Add bell peppers, carrots, and mustard greens, and cook while stirring for 3 minutes.
Stir in noodles, and add sauce to coat. Cook for another 2 minutes so that the flavors can meld. Garnish with spring onions, and serve immediately.