Season the chicken breasts with salt and pepper on both sides and set aside.
In a medium bowl, whisk together the chicken broth and cornstarch until smooth, then add heavy cream, Parmesan, garlic, oregano, thyme, and red pepper flakes. Whisk until well combined.
Place the seasoned chicken breasts in the crockpot and pour the sauce mixture over them.
Sprinkle the chopped sun-dried tomatoes over the chicken and sauce.
Cook on low for about 4 hours or on high for 2 hours until the chicken is tender.
About 30 minutes before serving, add the butter to the crockpot and stir it into the sauce.
Serve the chicken with the creamy sauce and garnish with fresh basil or parsley.