Combine CI1 (onions), CI2 (parsley, coriander), CI3 (vinegar, olive oil, spices, garlic), and CI4 (chicken breast) in a bowl; mix well and rest for 10 minutes.

Heat CI5 (oil) in a pan and grill the marinated chicken for 4 minutes on each side.

Reserve 2 tbsp of the marinade, pour it over the grilled chicken, and serve.