In a large soup pot, heat 2 tablespoons of olive oil and 1 tablespoon of butter over medium-high heat. Add diced celery, carrots, and onion. Sauté for 5-7 minutes until softened.

Stir in 3 cloves of minced garlic, cooking for an additional 30 seconds. Gradually sprinkle in 2 tablespoons of flour, stirring continuously to create a roux.

Slowly pour in 6 cups of chicken broth while stirring. Add 1 teaspoon of Italian seasoning along with the uncooked chicken breasts. Increase the heat and bring to a boil.

Reduce heat to low and cover the pot slightly ajar. Let the soup simmer for 15 minutes until the chicken is fully cooked.

Add 1 cup of orzo pasta to the pot, stirring gently. Cook uncovered for about 10 minutes, stirring occasionally until the pasta is tender.

Remove the chicken, chop it, and return it to the pot with the juice of one lemon and chopped parsley. Season with salt and pepper, then serve warm.