In a medium sized pan, bring water, chicken, green chili, salt and pepper to a boil on medium high heat. Once it comes to a boil, reduce the heat to low and cover. Let it cook for 15-20 minutes or until chicken is tender.
Remove the chicken pieces and add in chopped potatoes. Raise the heat to medium-high, once it comes to a boil, lower the heat. Let the potatoes cook uncovered for about 10-15 minutes. Meanwhile, shred the chicken. It should come to about a heaped cup of shredded chicken.
Blend the potatoes with the remaining water in a high-speed blender or food processor.
In a dutch oven or stock pot, melt butter over medium heat and add the chopped onion. Sauté until lightly golden and add garlic and ginger. Continue to sauté until the raw smell disappears. Add the chicken broth, blended potato stock mixture, corn, shredded chicken and soy sauce. Add a pinch of white pepper.
Turn off the heat. Slowly add in the egg while stirring so that it forms ribbon-like threads. Add the sesame oil, green onions or cilantro. Taste and adjust seasoning. Serve hot.