Start by spraying crock pot with Pam or other non-stick spray.
Add the chicken to the slow cooker. Sprinkle with salt and pepper.
Poke holes in the chicken with a fork and spread the pesto onto the chicken, which helps distribute the flavors better.
Juice 1/2 of a lemon and pour over the chicken, and cut the butter into slices and lay over the chicken as well.
Cover and cook on LOW for 4-5 hours without opening the lid during the cooking time.
At about the 4 hour mark, cook the pasta in salted water, according to the package directions, and drain well.
Shred the chicken with 2 forks (in a separate bowl if that's easier!). Add the cooked pasta, mozzarella, and parmesan cheese, stirring everything until the pasta is coated with the pesto sauce and the chicken is evenly dispersed throughout the pasta. Cover for about 10-15 more minutes or until the cheese has melted (may take longer for non-dairy cheeses, about 15-20).
Serve and enjoy!