In a large pot, heat a drizzle of olive oil over medium heat. Add diced onions, minced garlic, chopped carrots, and sliced celery, sautéing for about 5 minutes until softened and fragrant.

Add the boneless chicken breast to the pot, stirring to coat it with the sautéed vegetables. Pour in the low-sodium chicken broth and sprinkle in dried thyme. Bring to a gentle simmer over medium-high heat for 10 to 12 minutes.

Remove the chicken from the pot, allow it to cool slightly, then shred it using two forks. Return shredded chicken to the broth.

In a mixing bowl, combine all-purpose flour, baking powder, and a pinch of salt. In another bowl, whisk together an egg and milk, then fold this mixture into the dry ingredients until just combined.

Drop dollops of your dumpling batter into the simmering soup, spacing them evenly. Cover with a lid and allow the dumplings to steam for about 10 minutes.

Check the dumplings for doneness; they should be fluffy and cooked through. Adjust seasoning with salt and pepper to taste, then ladle the warm soup into bowls.