Heat olive oil in a large pot over medium heat; add diced chicken, onion, carrots, and celery, sautéing until the chicken is golden and vegetables soften.
Stir in the minced garlic, thyme, rosemary, sea salt, and black pepper, cooking for one minute until the spices become fragrant.
Pour in the chicken bone broth and bring the mixture to a gentle simmer.
In a small bowl, whisk the egg and cassava flour together to form a thick, sticky dough for the dumplings.
Use a small spoon to drop marble-sized portions of the dough into the simmering broth, covering the pot to steam for 5-7 minutes.
Stir in the Greek yogurt at the very end to create a creamy finish without boiling, then serve warm.