Place the raw, cubed chicken breasts, chopped onion, diced celery, diced potatoes, drained corn, chicken broth, dried thyme, garlic powder, salt, and pepper directly into the basin of a 5 or 6-quart slow cooker.

Stir all ingredients together gently to ensure the chicken is submerged in the liquid and seasonings are evenly distributed. Do not add the cream cheese or heavy cream yet.

Cover the slow cooker and cook on LOW for 6 hours or on HIGH for 3 to 3.5 hours, until the chicken is fully cooked and easily shreddable.

Remove the cooked chicken breasts from the slow cooker and shred them using two forks. Return the shredded chicken to the pot. Discard any remaining large pieces of celery or onion if desired, or enjoy as is.

Add the softened cream cheese cubes and heavy cream to the pot. Stir constantly until the cream cheese has melted completely and the chowder has thickened to a creamy consistency. This may take 5-10 minutes of gentle stirring.

Taste the chowder and adjust seasoning with additional salt and pepper if necessary. If the chowder is too thick, add a splash more broth or milk. Serve hot, garnished with fresh parsley or chives if desired.