Preheat your oven to 425°F (220°C). Toss chicken breasts with olive oil, salt, and pepper. Bake for 18-25 minutes until cooked through. Shred the chicken once cooled.

In a large pot, heat olive oil over medium heat. Add diced onion, chopped celery, and carrots; sauté for 5-6 minutes until softened. Stir in minced garlic and cook for an additional minute.

Add chicken broth and bring to a boil. Season with salt, pepper, and herbs as desired. Stir in orzo, then reduce heat and simmer for 8-12 minutes until tender.

In a bowl, whisk together egg yolks and lemon juice. Slowly add 1 cup of hot broth while whisking continuously to temper the eggs.

Gradually stir the tempered egg mixture into the pot. Add shredded chicken and mix well. Avoid boiling the soup after this step.

Ladle soup into bowls and garnish with fresh herbs, crumbled feta, and olive oil. Serve hot.