01 - Arrange chicken breasts at the bottom of the slow cooker. Season generously with salt, pepper, and Italian herbs, ensuring even coverage on all pieces.
02 - Scatter the chopped onion and minced garlic evenly over the seasoned chicken, creating a flavorful base layer.
03 - Pour the chicken broth and heavy cream over the ingredients. Distribute the cream cheese cubes and butter pieces across the top.
04 - Cover and cook on low heat for 4 hours, or until the chicken reaches an internal temperature of 165°F and is fork-tender.
05 - Transfer the cooked chicken to a cutting board. Using two forks, shred the meat into bite-sized pieces. Return the shredded chicken to the slow cooker, incorporating it into the sauce.
06 - Add the uncooked fettuccine to the slow cooker, stirring thoroughly to submerge the pasta in the liquid as much as possible.
07 - Sprinkle the freshly grated Parmesan cheese over the mixture and stir well to combine, allowing it to melt into the sauce.
08 - Cover and cook on high heat for 25 to 35 minutes, stirring once or twice during cooking, until the pasta is al dente and the sauce has thickened to a creamy consistency.
09 - Ladle the creamy chicken Alfredo into serving bowls and garnish with chopped fresh parsley. Serve immediately while hot.