Place the chicken breasts in the slow cooker in an even layer. Top with the diced onion and minced garlic.

In a bowl, whisk together the Alfredo sauce, heavy cream, parmesan cheese, Italian seasoning, paprika, salt, and pepper. Pour the mixture over the chicken.

Scatter the sun-dried tomatoes over the top.

Cover and cook on low for 3–4 hours, until the chicken is cooked through and tender.

During the last 30 minutes of cook time, remove the chicken and shred it with two forks. Return the shredded chicken to the slow cooker and stir to combine.

Cook the pasta according to package directions. Drain, then add the cooked pasta to the slow cooker and stir into the sauce.

Add the baby spinach, cover, and let it sit for about 5 minutes until the spinach has wilted.

Give everything a final stir, then top with fresh basil if desired before serving.