Heat the oil in a large frying pan, stir fry the peppers with a pinch of salt, and cook for 10 minutes. Remove from the pan.
Stir the onions into the same pan with the balsamic vinegar, cooking them gently till they wilt. Remove from the pan, adding them to the cooled peppers. Then add the tomatoes to the same pan and cook for 10 minutes. Stir in a teaspoon of thyme leaves and a teaspoon of finely chopped rosemary leaves with two of the cloves of garlic. Cook for a minute and then remove them from the pan. Add the olives to the same pan with a sprig of thyme, the remaining garlic and a few small bits of rosemary. Cook this for a minute and then add to the peppers and other ingredients. Combine them all and then serve them up on a platter.