Heat olive oil in a fry pan in medium heat.
Add chicken. Cook for about 5 minutes.
Turn over chicken and cook 2 minutes.
Stir-in onion. Cook until onion is clear.
Place chicken and sauteed onion in bowl.Sprinkle with salt and pepper.
Add vinegar, and chives.
Spread yogurt in every pita bread. Put the chicken mixture in each bread and the green chili.