Bring a large pot of water to a boil. Meanwhile, in a large, heavy skillet, heat the oil over medium-high until shimmering. Add the onion, garlic and ginger. Cook, stirring occasionally, until softened and lightly browned, about 5 minutes. Turn off the heat.
Add the noodles to the boiling water and cook according to package directions. Add the cabbage, bell pepper, mushrooms, snow peas and carrot; cook for 30 seconds. Drain the noodles and vegetables thoroughly.
Turn the heat under the skillet back to high. When the onions sizzle, add the soy sauce, sherry and sesame oil and let the mixture bubble for a few seconds. Add the noodles and vegetables; toss well. Cook, stirring often, until the mushrooms are fully cooked and the peppers are tender but still slightly crunchy, about 3 minutes.
Lower the heat to medium, add the chicken and cook, stirring often, to heat through. Season with salt and sprinkle with the peanuts.