Melt butter in a large Dutch oven over medium heat.
Add onion, carrots, and celery; sauté for 6 to 8 minutes until vegetables begin to soften.
Stir in minced garlic, thyme, and poultry seasoning; cook for 1 minute until fragrant.
Add chicken stock and water, then place the chicken thighs into the liquid.
Bring to a boil, then reduce heat to a simmer and cook for 20 minutes or until chicken reaches an internal temperature of 165°F.
Remove chicken from the pot and shred into bite-sized pieces using two forks.
Increase the heat to bring the liquid back to a rolling boil.
Add the frozen egg noodles and cook according to package directions, typically 15 to 20 minutes, until tender.
Return the shredded chicken to the pot and stir to combine.
Season with salt and black pepper to taste, then stir in fresh parsley before serving.