skin-on, bone-in chicken thighs (2 to 2 1/2 pounds) • Kosher salt and freshly ground pepper • extra-virgin olive oil • large sweet onion, cut into large chunks • cooking apples (see Notes), cut into chunks • ground ginger • garlic cloves, minced • low-sodium chicken broth • honey mustard • honey • unsalted butter, softened • all-purpose flour •