Chicken and Mushroom Fettuccini Alfredo

1 1/2 lbs. chicken breast tenders 2 pkgs (8 oz. each) mushrooms, cut in thirds (optional for our family, obviously) 1/2 tsp. salt 1/4 tsp. pepper 1/4 tsp. garlic powder 2 pkgs. (8 oz. each) cream cheese, cut into chunks 1 C. (2 sticks) butter, cut into pieces (I often cut back to 1 stick, without it tasting much different) 1 1/2 C. grated parmesan cheese, plus extra for garnish 1 1/2 C. whole milk 1 pkg. (1 lb.) fettuccini Spray inside of crockpot with cooking spray. Arrange chicken in single layer on bottom of crockpot. Top with mushrooms, sprinkle with salt, pepper, and garlic powder. Stir together cream cheese, butter, Parmesan, and milk in medium saucepan over medium heat. Whisk constantly until smooth and heated through. Pour over mushrooms, pushing down any that float to the surface. Cover and cook on low 4-5 hours or high 2 to 2 1/2 hours. It will take longer if you use boneless skinless chicken breasts like I do instead of the tenders. If using the chicken breasts, I pull them out at this point and break them up with forks before adding them back in to warm. Cook the fettuccini according to package directions in a saucepan, drain. Add to alfredo sauce and toss gently to combine. Serve with additional parmesan to combine. So not heart-healthy, but we lack a decent Italian restaurant, so this is my special occasion go-to recipe for Italian.