Begin by finely dicing the large yellow onion, medium carrots, and celery stalks into small, even pieces to ensure they cook uniformly. Mince the garlic cloves and grate the sharp cheddar and Monterey Jack cheeses. Gather all your ingredients on the counter for easy access as you create your delicious Creamy Chicken Macaroni Cheese Soup.

In a large pot, melt 4 tablespoons of unsalted butter over medium heat until frothy. Add the diced onion, carrots, and celery, sautéing for 8-10 minutes until the vegetables are tender and the onion is translucent. Stir in the minced garlic, dried thyme, smoked paprika, and mustard powder, cooking for an additional 2 minutes, allowing the spices to release their wonderful aroma.

Sprinkle ¼ cup of all-purpose flour into the pot with the vegetables, stirring continuously for about 2-3 minutes until the mixture turns lightly golden and forms a roux. Gradually whisk in 6 cups of low-sodium chicken broth, followed by 2 cups of whole milk and 1 cup of heavy cream. Bring the mixture to a gentle simmer while stirring frequently until it achieves a smooth consistency.

Lower the heat to medium-low; add the grated sharp cheddar and Monterey Jack cheeses gradually, stirring continuously until melted and fully incorporated into the soup. Take care not to let the soup boil at this point to prevent curdling. The Creamy Chicken Macaroni Cheese Soup should now have a velvety texture and rich cheesiness.

In a separate pot, bring water to a boil and cook 1 ½ cups of elbow macaroni according to package instructions until al dente. Drain the cooked pasta and set it aside. This step ensures your macaroni maintains the perfect texture without becoming mushy when combined with the soup.

Add the cooked chicken and drained macaroni to the pot with the creamy soup mixture. Warm everything on low for 5-10 minutes until heated through, stirring occasionally. Taste and adjust seasoning with salt and freshly ground black pepper as desired. Ladle the comforting Creamy Chicken Macaroni Cheese Soup into bowls, garnishing with optional toppings like fresh parsley or crispy bacon for added flavor and presentation.