Dice the chicken breast into bite-sized pieces and finely chop the carrots, celery, and onion.
Heat the olive oil in a small pot over medium heat and sauté the onion, carrots, and celery until the onion is translucent.
Add the chicken pieces to the pot and cook until browned on all sides, then season with half of the sea salt and black pepper.
Pour in the chicken broth and add the fresh thyme, bringing the mixture to a gentle simmer.
While the broth simmers, whisk together the whole wheat flour, baking powder, and the remaining salt and pepper in a small bowl.
Stir the Greek yogurt into the flour mixture until a soft dough forms; if it is too dry, add a teaspoon of water.
Drop small spoonfuls of the dough onto the surface of the simmering broth, then cover the pot with a tight-fitting lid.
Steam the dumplings for 8 to 10 minutes without lifting the lid, until they are puffed and cooked through.
Ladle the chicken, vegetables, and dumplings into a bowl and serve immediately.