In a large soup pot, melt the butter over medium heat. Add the diced onions, carrots, and celery. Sauté for about 4 minutes until softened. Add garlic and cook for another 1 minute.
Stir in the seasonings (basil, parsley, oregano, thyme, mustard powder, pepper), soy sauce, hot sauce, chicken, and chicken broth.
Bring the soup to a gentle simmer (avoid boiling to keep the chicken tender) and cover partially. Let it cook for about 15-20 minutes until the chicken is fully cooked. Remove the chicken, shred it with two forks, and discard the bones. Return the shredded chicken to the pot.