1. 1. Prepare the Chicken: Pat the chicken pieces dry with paper towels. Season them generously with salt and pepper. This step is crucial for developing a good sear and locking in flavor.

2. 2. Sear the Chicken: Heat the olive oil in a large oven-safe skillet (cast iron or stainless steel works best) over medium-high heat. Once the oil is shimmering, add the chicken in a single layer, making sure not to overcrowd the pan. Cook for 3-4 minutes per side, until golden brown. The chicken doesn’t need to be cooked through at this point; you’re just looking for a nice sear. Remove the chicken from the skillet and set aside.

3. 3. Saute Aromatics: Reduce the heat to medium. Add the chopped onion to the same skillet, scraping up any browned bits from the bottom of the pan. Cook for 3-5 minutes until the onion softens and becomes translucent. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.

4. 4. Deglaze and Build the Sauce: Pour in the apple cider and chicken broth, stirring well to deglaze the pan and incorporate all the flavorful browned bits. Stir in the Dijon mustard and dried thyme. Bring the mixture to a simmer.

5. 5. Simmer and Thicken (Optional): Return the seared chicken to the skillet. Add the diced apple. Reduce the heat to medium-low, cover the skillet, and let it simmer for 10-12 minutes, or until the chicken is cooked through and reaches an internal temperature of 165 F (74 C). If you prefer a thicker sauce, in a small bowl, whisk together the cornstarch and cold water to create a slurry. Stir the slurry into the simmering sauce and cook for another 1-2 minutes, stirring constantly, until the sauce thickens to your desired consistency.

6. 6. Finish and Serve: Taste the sauce and adjust seasonings if needed. Garnish generously with fresh chopped parsley before serving.