1. Place the chicken breast and salt in a medium saucepan and cover with water. Cover and simmer over medium-low heat until fully cooked, about 25 minutes.
2. Remove the chicken from the pot, reserving the liquid. When the chicken is cool enough to be handled, shred it.
3. Keep two cups of liquid from the poached chicken and discard the rest. Add sugar, soy sauce, garlic, ginger, mirin, and sesame oil to the liquid in the pot and bring to a boil. Mix the cornstarch with cold water until dissolved and add to the boiling sauce. Cook until thickened, about three more minutes.
4. Return the shredded chicken to the sauce. Serve with crispy fried onions and sesame seeds sprinkled on top.