Heat a large Dutch oven over medium-high heat. Add 1 tablespoon olive oil and heat for about 1 minute. Add the sliced celery, diced carrots, and diced onion. Cook for 5 minutes, stirring occasionally, until the onion is soft and translucent. Add 3 cloves minced garlic and cook for an additional 1 minute until fragrant.
Add 3 boneless skinless chicken breasts to the pot and season with 1 teaspoon salt and 1/2 teaspoon black pepper. Pour in 8 cups chicken broth and bring to a boil.
Boil for 15 to 20 minutes, or until the chicken is cooked through and shreds easily with a fork. Using two forks, shred the chicken directly in the pot or remove to a cutting board to shred, then return it to the pot.
In a medium-sized mixing bowl, whisk together the 2 cups all-purpose flour, 3 teaspoons baking powder, and 1 teaspoon salt. Gradually add 1 cup buttermilk, stirring until well combined.
Drop spoonfuls of the dumpling batter directly into the simmering soup. Cover the pot and let simmer for 20 minutes, until the dumplings are fluffy and steamed.
Ladle the chicken and dumplings into bowls and serve hot.