Season both sides of the chicken with salt and pepper.
Heat 1/2 the oil in a large, deep frying pan over high heat. Add chicken. Cook for about 45 seconds each side or until browned and just cooked through. Transfer to a plate.
Add remaining oil to pan. Reduce heat to medium-high. Add the onion, garlic and dried oregano. Cook, stirring, for 2 minutes 30 seconds. Add passata, sugar, tomatoes and olives. Bring to a simmer. Cook for 5 minutes, stirring occasionally. Season with salt and pepper.
Return chicken to pan. Cook for 1 to 2 minutes or until chicken is heated through. Sprinkle with fetta. Top with fresh oregano. Serve with pita bread.