Infuse The StockPlace the roasted chicken carcass in a large pot. Add black peppercorns, green leek top, bay leaf, halved carrot, quartered onion, and parsley stalks. Pour hot chicken stock over the ingredients. Please bring it to a gentle simmer, allowing the flavors to meld for about 30 minutes.
Strain The BrothOnce infused, strain the stock through a fine mesh strainer, ensuring you capture all those rich flavors. Discard the solids and set the clear, aromatic broth aside.
Prepare The RouxIn the same pot, melt butter over medium heat. Add the chopped onion and sauté until it turns translucent. Sprinkle in the plain flour, stirring continuously to form a roux. Cook for a couple of minutes to eliminate the raw taste of the flour.
Introduce The BrothGradually pour the prepared chicken stock into the pot, whisking continuously to avoid lumps. Let the mixture simmer until it thickens, creating a velvety base for your soup.
Add Vegetables And ChickenStir in the diced carrot and potatoes. Let them cook until tender, infusing the soup with their natural sweetness. Add the leftover chicken, allowing it to warm through and become one with the broth.
Incorporate Milk And FinishPour in the milk, bringing a creamy texture to the soup. Allow it to simmer gently, enhancing the flavors. For an extra touch of indulgence, swirl in double cream if desired.
Garnish And ServeLadle the creamy chicken soup into bowls. Top each serving with extra pieces of leftover chicken and a sprinkle of finely chopped curly parsley. The vibrant colors and fresh herbs add a delightful finishing touch.