Heat the oil over medium/high heat in a large skillet until hot but not smoking. Add the onion and cook for 3-4 mins, until the onion is golden, stirring frequently.
Add the garlic and cook an additional 1-2 mins. Stir in the herbs and spices and toast for 1-2 mins. Add the tomato paste and then fill the tomato paste can with water and add that to the pan.
Mix in the chiles, vinegar, sugar, stock, salt and pepper and bring to a boil. Reduce to a simmer and add the chicken breasts in a single layer and cover the chicken with the sauce.