Preheat oven to 400 F. Season chicken thighs with olive oil, garlic powder, onion powder, salt, and pepper. Transfer to a baking dish and bake for 30 minutes or until internal temperature reaches 165 F.
Meanwhile, chop onion, carrots, celery, and garlic.
Heat 1 tbsp olive oil in a large pot on medium heat. Add the chopped onion, celery, and carrots. Stir and sauté for 5 minutes. Then add in the chopped garlic and stir for 1 minute.
Add in the chicken broth and increase the temp to high heat. Once liquid is boiling, add the orzo pasta and cook according to package instructions.
While orzo cooks, whisk one whole egg and two egg yolks in a medium bowl. Whisk in juice from 1 ½ lemons. Season with salt and pepper.
Reduce heat under orzo to low. Using a ladle, scoop out 1 cup of warm broth. Pour it into the egg/lemon mixture while simultaneously whisking, tempering the eggs.
Slowly pour the tempered egg mixture back into the pot with orzo while whisking continuously.
Once the chicken is cooked, remove from oven and use two forks to shred chicken into pieces.
Mix shredded chicken into the soup and bring the heat back up to medium. Let that simmer for 5 minutes, stirring often.
Taste and season with more salt & pepper if needed. Garnish with fresh dill or more lemon, optional.