Place the chicken breasts or thighs in the bottom of the crockpot.
Add the chicken broth, minced garlic, butter, salt, and pepper.
Cover and cook on low for 4-5 hours or high for 2-3 hours, until the chicken is fully cooked and tender.
Once the chicken is cooked, remove it from the crockpot and shred it with two forks. Set it aside.
Add the cream cheese, heavy cream, and Parmesan cheese to the crockpot.
Whisk the mixture until smooth, letting the residual heat melt the cheese.
While the sauce is coming together, cook the pasta according to the package instructions. Drain and set aside.
Return the shredded chicken to the crockpot and stir to coat it in the Alfredo sauce.
Add the cooked pasta to the crockpot and toss until evenly coated.
Transfer the chicken Alfredo to serving bowls or plates.
Top with extra Parmesan cheese and optional red pepper flakes. Enjoy!