Start by patting the chicken breasts dry with a paper towel to ensure a good sear. Season both sides generously with salt, pepper, Italian seasoning, and onion powder for a flavorful base.
Heat the olive oil in a skillet over medium heat. Once the oil is shimmering, carefully place the seasoned chicken breasts in the skillet. Sear them for 3-4 minutes on each side until they develop a beautiful golden brown crust.
Once the chicken is seared, transfer it to the slow cooker. Scatter the minced garlic evenly over the top of the chicken for an aromatic flavor boost.
Pour the chicken broth over the chicken, ensuring that the chicken is partially submerged in the broth to keep it moist while cooking.
Cover the slow cooker with its lid and set it to cook on low for 6-7 hours or on high for 3-4 hours.
About 30 minutes before you’re ready to serve, stir in the freshly grated Parmesan cheese into the slow cooker.
If you prefer a thicker sauce, mix the cornstarch with a small amount of water to form a slurry. Stir this into the slow cooker and allow it to cook for an additional 15 minutes until the sauce thickens to your liking.
Taste the sauce and adjust seasoning if needed. Carefully lift the chicken out of the slow cooker, slice if desired, and generously spoon the creamy garlic Parmesan sauce over the chicken.
To finish, sprinkle chopped fresh parsley over the dish.