Mash olives and lemon with a knife, remove the bones and finely chop.

Cut the potatoes into small pieces or cut them in half lengthwise if the potatoes are not very large. Transfer to a bowl and mix with chopped olives, butter, zest of one lemon, cumin, 0.5 teaspoon salt and 0.25 teaspoon black pepper. Sprinkle with lemon juice. Mix well and place in a deep frying pan. Add water and bring to a boil.

Cover with a lid and cook over medium heat for 10-12 minutes until the potatoes are tender. Remove the lid and cook another 1-2 minutes until the water has evaporated. Serve sprinkled with parsley.