Step 1: Preheat and Pat Dry
Preheat your oven to 400°F (200°C). This high heat will help crisp the skin and cook the chicken through. Use paper towels to pat the chicken thighs completely dry. This is the most crucial step for achieving crispy, not steamed, skin. Season both sides generously with kosher salt, black pepper, garlic powder, onion powder, and smoked paprika.

Step 2: Sear the Chicken to Perfection
Heat the olive oil in a large, oven-safe skillet (cast iron is ideal) over medium-high heat. Once the oil is shimmering, place the chicken thighs in the pan, skin-side down. Do not overcrowd the pan; work in batches if necessary. Sear, without moving them, for 6-8 minutes, until the skin is deeply golden brown and crispy. Flip and sear for another 2-3 minutes on the other side. Remove the chicken to a plate and set aside.

Step 3: Sauté the Aromatics
Reduce the heat to medium. In the same skillet, with all the delicious chicken drippings, add the sliced onion. Sauté for 4-5 minutes until softened and beginning to caramelize. Add the minced garlic and cook for another minute until fragrant. Add the sliced apples and fresh herb sprigs, cooking for 2-3 minutes to slightly soften the apples.

Step 4: Create the Braising Liquid
Pour the apple cider and chicken broth into the skillet. Using a wooden spoon, scrape up all the browned bits (the fond) from the bottom of the pan—this is packed with flavor. Whisk in the whole grain mustard, Dijon mustard, apple cider vinegar, and maple syrup (if using). Bring the liquid to a gentle simmer.

Step 5: Braise in the Oven
Nestle the seared chicken thighs back into the skillet, skin-side up, so the skin remains above the liquid to stay crisp. Transfer the entire skillet to the preheated oven.

Step 6: Cook to Juicy Perfection
Bake, uncovered, for 25-30 minutes, or until the chicken thighs are cooked through (internal temperature of 165°F / 74°C) and the sauce has reduced slightly.

Step 7: The Grand Finale – Sauce and Serve
Carefully remove the hot skillet from the oven. Transfer the chicken, apples, and onions to a serving platter. Place the skillet back on the stovetop over medium heat. Bring the sauce to a simmer and let it reduce for 3-5 minutes until it thickens to a glaze-like consistency that coats the back of a spoon. Remove from heat and swirl in the tablespoon of cold butter. This final step, called monter au beurre, gives the sauce a beautiful sheen and a velvety texture. Taste and adjust seasoning. Pour the glorious sauce over the chicken on the platter, garnish with fresh herbs, and serve immediately.