Heat olive oil in a large pot over medium heat.
Add diced onion, sliced carrots, and sliced celery to the pot. Sauté for 5-7 minutes until vegetables are softened.
Add minced garlic and cook for 1 minute until fragrant.
Pour in the chicken broth and bring the mixture to a boil.
Add shredded cooked chicken, dried thyme, dried parsley, salt, and black pepper to the pot. Stir to combine.
Add the egg noodles and cook for 7-8 minutes until tender.
While the noodles cook, prepare the dumpling batter: In a medium bowl, whisk together flour, baking powder, and salt.
Add milk and melted butter to the dry ingredients and stir until just combined. Do not overmix.
Once noodles are tender, drop spoonfuls of dumpling batter (about 1 tablespoon each) onto the surface of the simmering soup.
Cover the pot with a lid and simmer for 12-15 minutes without lifting the lid, until dumplings are cooked through and fluffy.
Remove the soup from heat and let it rest for 5 minutes before serving.
Ladle soup with dumplings into bowls and serve warm.