Prep the chicken. Pat the chicken thighs dry with paper towels. Season both sides generously with salt and black pepper. Dry skin helps you get good browning.

Brown for flavor. Heat a large, heavy skillet or Dutch oven over medium-high heat. Add a splash of oil. Place chicken skin-side down and cook until the skin is deeply golden and crisp, about 6–8 minutes. Flip and brown the other side for 3–4 minutes. Transfer to a plate.

Soften the aromatics. Pour off excess fat, leaving about 1 tablespoon in the pan. Add sliced onions and a pinch of salt. Cook over medium heat until softened and lightly caramelized, 6–8 minutes. Stir in minced garlic and cook 30 seconds until fragrant.

Deglaze with vinegar. Add 1/2 cup apple cider vinegar to the hot pan. Scrape up the brown bits with a wooden spoon. Let it bubble for 1–2 minutes to soften the acidity.

Build the braising liquid. Stir in 1 cup chicken stock, 1 teaspoon Dijon mustard, a few sprigs of thyme or rosemary, and 1 bay leaf. If using, add thin apple slices. Taste and adjust with a pinch of salt.

Nestle the chicken back in. Return the thighs to the pan, skin-side up. The liquid should come about halfway up the sides of the chicken. If not, add a splash more stock or water.

Braise gently. Bring to a low simmer, then cover and cook over low heat for 25–30 minutes, or until the chicken is very tender and cooked through. Aim for a gentle bubble, not a hard boil.

Reduce the sauce. Remove the lid and let the sauce simmer for another 5–10 minutes to thicken slightly. For a richer finish, stir in 1 tablespoon of butter. Taste and adjust seasoning, adding a small splash of vinegar if you want more brightness.

Serve. Spoon onions and sauce over the chicken. Garnish with fresh herbs. Serve with mashed potatoes, polenta, rice, roasted vegetables, or crusty bread.