Sprinkle chicken with thyme, salt and pepper.
In large fry-pan, heat half of the oil over medium high heat; brown chicken all over.Transfer to plate. Add remaining oil to fry-pan.
Cook apples and onion, stirring occasionally, until golden, about
Add apple cider, bring to boil, stirring and scraping up brown bits from pan.
Return chicken to fry-pan.
Cover and cook over medium low heat, turning once, until no longer pink inside (about 7 minutes).
Transfer chicken to serving platter.
Whisk vinegar with cornstarch; whisk into fry-pan and cook, stirring, until glossy and thickened (about 1 minute).
Pour over chicken.