How to Make It
Place the potatoes in a large pot and add 2 teaspoons salt and enough cold water to cover. Bring to a boil. Reduce heat and simmer until the potatoes are very tender, 20 to 25 minutes. Reserving ½ cup of the cooking water, drain the potatoes and return them to the pot.
Add the olive oil, zest, reserved cooking water, 1 teaspoon salt, and ¼ teaspoon pepper to the potatoes and mash to the desired consistency. Fold in the olives.