If using raw chicken, season with a little salt and pepper, then sauté in the pot until cooked through. Remove from the pot, let cool slightly, and shred or dice. Set aside. If using pre-cooked chicken, you can skip this step.
In a large pot, heat the butter or olive oil over medium heat. Add the sliced leeks and cook, stirring occasionally, for about 5-6 minutes or until soft and fragrant.
Add carrots, and celery, and cook for another 3-4 minutes, until the vegetables begin to soften.
Pour in the chicken or vegetable broth, and bring the soup to a boil. Reduce heat to low, cover, and let simmer for about 20 minutes or until the carrots and celery are tender.
Stir in the cooked, shredded chicken and let it heat through for a few minutes. Taste the soup and season with salt and pepper as needed.
Add Cream (Optional):
If you’d like a creamy texture, stir in the heavy cream or milk and let it gently warm for 2-3 minutes. Don’t let it boil.
Serve the soup into bowls and garnish with fresh parsley or thyme. Serve with crusty bread for dipping.