Pat the chicken breasts dry and season with salt, pepper, and garlic powder. Heat olive oil in a skillet over high heat and quickly sear chicken on both sides.

Place seared chicken in the slow cooker. Add sliced sausage, heavy cream, chicken broth, butter, smashed garlic cloves, Cajun seasoning, and a pinch of salt and pepper.

Cover and cook on low for 4 hours or on high for 2–3 hours, until chicken reaches 165°F. Remove the chicken and let it cool slightly before slicing.

Add the 1/2 cup hot water and uncooked penne pasta to the slow cooker. Stir to combine, then cover and cook on high for about 30 minutes, or until the pasta is tender.

In a small bowl, whisk together cornstarch and 2 tablespoons of water. Stir the slurry into the slow cooker to thicken the sauce. Let it cook a few more minutes.

Stir in mozzarella and Parmesan cheese along with the sliced chicken. Mix everything well to melt the cheese and coat evenly.

Top with extra Cajun seasoning and garnish with fresh parsley before serving.