01 - Melt butter in a large pot or deep skillet over medium heat. Add onions, carrots, and celery; sauté for 4–5 minutes until softened.
02 - Stir in garlic and cook for 1 minute until fragrant.
03 - Sprinkle flour over the vegetables and stir to coat evenly. Cook for 1 minute to remove the raw flour taste.
04 - Slowly whisk in chicken broth, then add milk. Bring the mixture to a gentle simmer while stirring constantly.
05 - Add orzo, thyme, parsley, salt, and pepper. Reduce heat to medium-low and simmer uncovered for 10–12 minutes, stirring occasionally until orzo is al dente and the sauce has thickened.
06 - Stir in heavy cream, cooked chicken, and peas. Simmer for 3–5 minutes until heated through. Remove from heat, let stand for 2–3 minutes to thicken, and garnish with extra parsley.