Prep the chicken for the best texture. Pat the chicken breasts dry with paper towels. This removes excess moisture so the sauce stays creamy instead of watery. If your chicken breasts are very thick, you can pound them lightly to a more even thickness for consistent cooking.
Season the chicken evenly. Sprinkle both sides with salt, black pepper, Italian seasoning, and paprika (if using). Press the seasoning gently into the surface so it stays on during slow cooking and flavors the sauce.
Layer in the slow cooker. Place the seasoned chicken in the bottom of the crockpot in a single layer. Scatter the minced garlic over the top, then place the sliced butter pats across the chicken so it melts and bastes the meat as it cooks.
Add liquid without washing off seasoning. Pour the chicken broth around the edges of the crockpot (not directly on top of the chicken). This keeps the seasoning in place while still providing enough liquid to create a rich garlic butter base.
Slow cook until tender. Cover and cook on LOW for 4 to 5 hours, or until the chicken reaches 165°F and is fork tender. LOW heat is strongly recommended for cream-based crockpot meals because it produces juicier chicken and reduces the chance of sauce separation.
Stir and prepare to finish the sauce. When the chicken is done, gently spoon some of the buttery cooking liquid over the top and give the liquid a careful stir to combine the melted butter and broth. If you want shredded chicken, remove the chicken briefly, shred with two forks, then return it to the crockpot.
Add cream at the right time for a smooth finish. Pour in the heavy cream and sprinkle in the Parmesan cheese. Stir slowly until the Parmesan melts into the sauce. If using red pepper flakes, add them now. Cover and cook for 20 to 30 minutes more on LOW so the sauce becomes silky and cohesive.
Adjust consistency if needed. If the sauce seems too thin, leave the lid slightly ajar for 10 to 15 minutes to allow gentle reduction. If it becomes too thick, add a small splash of broth and stir until it loosens. Taste and adjust salt and pepper as needed.
Serve with plenty of sauce. Spoon chicken into bowls or plates and ladle the garlic butter cream sauce over the top. Finish with fresh chopped parsley. Serve over mashed potatoes, rice, or buttered noodles. For a lower carb option, serve with roasted vegetables or cauliflower mash.