Dice the celery into 1/4-inch pieces, slice the carrots into 1/4-inch rounds, and finely dice the onion. Mince the garlic cloves and set aside separately—garlic burns easily, so it needs to be added after the other aromatics have softened. Having everything prepped and ready before you start cooking ensures smooth, uninterrupted timing and helps build a flavorful foundation for the soup.

Heat the butter and olive oil in a large pot over medium heat until the butter is foaming. Add the diced celery, sliced carrots, and onion, stirring occasionally, and cook for 5-7 minutes until the vegetables are softened and lightly caramelized—this develops deeper flavor. Add the minced garlic and cook for just 30 seconds, stirring constantly to prevent burning. Sprinkle the flour over the vegetables and stir continuously for 1 minute to create a light roux, which will help thicken the soup and add a subtle savory depth.

Gradually pour in the chicken broth while stirring to prevent lumps from forming in the roux. Add the Italian seasoning and dried thyme, then nestle the 1-inch chicken chunks into the broth. Increase the heat to bring the soup to a gentle boil, then immediately reduce to a simmer. I find that cutting chicken into smaller pieces helps it cook evenly and infuse flavor into the broth more quickly.

Cover the pot and simmer for 15 minutes. The chicken should be cooked through and tender, and the vegetables will continue to soften. Check that the chicken shows no pink in the center—it should be opaque throughout.

Stir in the orzo pasta and return the soup to a gentle simmer. Cook uncovered for about 10 minutes, stirring occasionally, until the orzo is tender but still has a slight bite. The starch from the orzo will slightly thicken the broth as it cooks, giving the soup a more luxurious mouthfeel.

Add the lemon juice and fresh parsley, then taste and season generously with salt and pepper. I always add lemon juice at the end rather than early on because it brightens the flavors without becoming harsh or fading during the long cooking time. Stir gently to combine and adjust seasonings to your preference—the soup should taste bright, savory, and well-balanced.

Ladle the hot soup into bowls and serve immediately while the orzo is tender and the broth is steaming. The soup is best enjoyed fresh, though it can be stored in the refrigerator for 3-4 days.