Heat the olive oil in a large skillet over medium-high heat. Season the chicken breasts with salt and pepper, then add them to the skillet. Cook the chicken for 6-7 minutes per side, until golden brown and cooked through (internal temperature of 165°F/74°C). Remove the chicken from the skillet and set it aside.

1. In the same skillet, add the chopped onion and cook for 3-4 minutes, until softened. Add the minced garlic and cook for an additional 30 seconds, until fragrant.
2. Pour in the apple cider and chicken broth, scraping up any browned bits from the bottom of the skillet. Stir in the thyme and bring the mixture to a simmer. Let it cook for 5-7 minutes, allowing the sauce to reduce slightly.
3. Lower the heat to medium and stir in the heavy cream and Dijon mustard. Let the sauce simmer for 2-3 minutes, until it thickens and becomes creamy.
4. Return the cooked chicken breasts to the skillet, spooning the sauce over the top. Let the chicken simmer in the sauce for another 3-4 minutes, until heated through and coated in the creamy sauce.
5. Finish by stirring in the butter to add richness to the sauce.
6. Serve the creamy apple cider chicken with a sprinkle of fresh parsley for garnish, and enjoy with mashed potatoes, rice, or a side of sautéed vegetables.