Sear the Chicken: Heat oil in a large skillet over medium-high heat. Season chicken with salt and pepper, then sear on both sides until golden brown (about 3-4 minutes per side). If necessary, cook in batches to avoid overcrowding.
Prepare the Sauce: In a bowl, whisk together the heavy cream, chicken broth, cornstarch, garlic, parsley, salt, and pepper.
Slow Cook: Place the seared chicken breasts in a 2.5- to 4-quart slow cooker. Pour the prepared sauce over the chicken, ensuring it's evenly coated
Cook: Cover and cook on low for about 3 hours, or until the chicken reaches an internal temperature of 165°F (75°C). Cooking times may vary slightly depending on your slow cooker.
Serve: Spoon the creamy garlic sauce over the chicken and serve. This dish pairs beautifully with pasta, rice, or mashed potatoes.