Season chicken breast with salt, pepper, garlic powder and place in oven heated to 425 degrees, for 30 minutes. After 30 minutes, turn oven down to 325 degrees, add 2 cups of water to roasting pan and cover with foil, sealing the edges. Cook for an hour, then let the chicken cool in the covered pan for an hour or more.
While the chicken is cooling, saute the diced onion in the olive oil until it is transparent. Add the carrots and continue to cook. After 10 minutes add the chicken broth with salt and pepper to taste. Cook for 30 minutes. While the soup is cooking, shred and cut up the chicken breast, add to the pot. Add the chopped parsley. Check seasonings before serving.