In a large skillet or non-stick pan, heat the oil over medium heat. Season chicken generously with salt and pepper and sear on both sides until deep golden brown, about 4 minutes per side. Transfer chicken to a plate.
Add the garlic to the skillet and cook for 1-2 minutes until it starts to turn golden brown. Stir in broth, cream, thyme, red pepper flakes (if using), and sundried tomatoes. Simmer for 5 minutes, stirring often.
Return chicken to skillet and spoon sauce all over the chicken breasts. Simmer until the chicken reaches an internal temperature of 160°F using a thermometer and the sauce is thick and smooth. Remove from heat and stir in the parmesan.