tbspolive oil - adjust the amount based on the moisture of the potatoes.
Peel the potatoes and boil them together with the garlic until they are tender.
While the potatoes boil, cut the fish into small pieces and finely chop the rosemary leaves.
When the potatoes are done mix/mash them in the remains of the boiling water and add the olive oil, rosemary, sliced black olives and pieces of fish. Let all this boil until the fish is tender - about 5 minutes.
Serve in a deep dish with a little olive oil on top, and grilled bread on the side.