Cut chicken into bite-sized pieces. Slice onion and carrot into thin long pieces. Heat a deep pan and saute the chicken, onion, and carrot. Salt the ingredients. Add in the pan and simmer until ingredients are soften. Add curry roux in the soup and bring to a boil. Add potatostarch and water mixture in the soup to thicken. Add udon noodles in the curry soup and heat. Add soy sauce in the udon soup and sprinkle chopped green onion over it.