How to Make It
Preheat oven to 325°
Season the chicken thighs with salt and pepper. In a large skillet or Dutch oven set over medium-high heat, add the oil and heat until shimmering. Brown the thighs skin side down, about 5 minutes. Turn over and brown all other sides, about another 5 minutes.
Drain off most of the rendered fat, then add the onion. Reduce the heat to medium. Cook, stirring, until the onion is fairly soft and translucent, about 10 minutes. Add rosemary leaves and cook 1 minute. Add 2 cups cider and bring to a boil. Reduce by half, about 5 minutes. Add the chicken thighs, then cover the pan and place in the oven. Cook for 15 minutes then flip each piece. Add the apples, cover the pan again and cook until the thighs are tender and falling off the bone, about another 15 minutes.
Skim off most of the fat from the sauce, then serve the thighs in bowls with the sauce.