Rinse briefly the olives under running water, drain and dry completely on paper towels.

Heat about 1/2 inch olive oil in a frying pan.  Add the onion slices and sauté for 3-4 minutes, to soften.  Add the olives and sauté stirring often, for about 5 minutes, or until puffed and shiny. 

With a slotted spoon transfer the olives and onion to a bowl, add the herbs, toss well, and serve warm or at room temperature. 
If you like, place a thin slice of cheese on each bread slice, and top with the fried olives and onions.