Chicken Alfredo Fettuccine

Heat 2 tablespoons of unsalted butter in a large cooking vessel over medium heat. Introduce boneless, skinless chicken into the pan and add half of the minced garlic along with a pinch of dried Italian herbs. Allow the chicken to cook until it reaches an internal temperature of 165 degrees Fahrenheit (74 degrees Celsius), indicated by the absence of pink coloration in its center and clear, flowing juices. Remove the chicken from the pan and set it aside for later use.

Prepare a large container with salted water, then bring the liquid to a vigorous boil. Cook fettuccine pasta in the boiling water until it reaches an optimal level of doneness, characterized by a slight firmness to the bite when bitten into. Allow it to cook for 8 to 10 minutes before draining excess water.

Meanwhile, melt the remaining 4 tablespoons of unsalted butter in the same cooking vessel. Introduce sliced onions and button mushrooms into the pan along with the remaining minced garlic; sauté until the onions have lost their translucent appearance, approximately 5 minutes. Stir in flour, salt, and pepper; cook for an additional 2 minutes. Gradually add milk and half-and-half to the pan, stirring constantly until a smooth, creamy sauce is achieved. Stir in both types of cheese until they have fully melted.

Combine the cooked chicken mixture, diced tomatoes, and sour cream in the pan. Serve the sauce over cooked fettuccine pasta.