Line a large rimmed baking sheet with unbleached parchment paper, and place the chicken breasts on top.
Sprinkle the salt and pepper on both sides of the meat, and drizzle with the olive oil.
Place in the center of the preheated oven and bake until the chicken is cooked through and registers 165°F on an instant-read thermometer (25 to 35 minutes, depending upon the thickness of the meat).
Once the chicken is cooked, remove it from the oven and cut it into 1/2-inch cubes. Set the chicken aside. The chicken can be made ahead of time and stored in a sealed container in the refrigerator for up to 2 days.
Make the soup.
In a large, heavy-bottom stockpot, heat the olive oil over medium heat, then add the carrots, celery, onion, salt and pepper, and stir to combine.
Cook, stirring occasionally, until the vegetables are all fork-tender (about 8 minutes). You can also reduce the heat to low, cover the pot, and cook for 10 minutes.
Push the vegetables to the side of the saucepan, and place the butter in the center. Melt the butter over medium heat.
Add the flour blend and whisk until well-combined. Continue to cook, whisking occasionally, until the mixture starts to simmer and smell fragrant (about 2 minutes). The mixture will first clump and then smooth out.
Slowly add the chicken stock, and then the milk and the herbs, whisking constantly, until well-combined.
Bring the mixture to a simmer, stirring occasionally, until it begins to thicken (about 8 minutes).
Add the cooked chicken, and mix to combine. The soup portion is now complete.
Prepare the dumpling mixture.
In a medium-size bowl, place the flour blend, xanthan gum, cornstarch, baking powder, and salt, and whisk to combine.
Create a well in the center of the dry ingredients, add the eggs and milk, and mix to combine. The batter will be thick.
Cook the dumplings in the soup.
Using a large spring-loaded ice cream scoop or two large spoons, scoop the dumpling batter into the hot soup in portions that are about 1/4-cup each.
Stir gently after every few additions to prevent the dumplings from sticking to the bottom of the pot or each other.
Cover the pot and cook, stirring occasionally to turn the dumplings, for 15 to 20 minutes or until they are cooked all the way through. They will be firm and a toothpick inserted in the center of any of the dumplings should come out clean.
Serve hot.
Video
Notes
For the flour blendYou can also use Nicole's Best multipurpose gluten free flour blend for soup in place of the basic gum-free flour blend. Do not add any xanthan gum; just use 1/2 cup or 70 grams, as directed.You can also use Nicole's Best for the dumplings in the same manner, gram for gram. Add 7/8 teaspoon, which is just 1/8 teaspoon less than 1 teaspoon, or 1 scant (underfull) teaspoonful.Tips for other varietiesFor the “Quick Chicken and Dumplings” method, in place of the butter, flour, stock and half and half, use 6 cups (48 fluid ounces) of chicken stock and 1 recipe (about 24 ounces) gluten free cream of chicken soupFor the “Slow Cooker Chicken and Dumplings” method, eliminate the butter as an ingredient. Add 1 1/2 cups (9 ounces) peeled and shredded russet potatoes to the vegetables. In place of the half and half, use 3 cups of milk and one 12-ounce can of evaporated milk.