Place potatoes in a large saucepan, and cover with water; bring to a boil. Cover, reduce heat, and simmer 15 minutes or until potatoes are tender.
Drain potatoes well; return to pan.
Add milk and olive oil to hot potatoes, and coarsely mash. Fold in cheese, salt, and pepper.
Add just enough water to cover the potatoes. Any more will only lengthen the time it takes to bring the water to a boil, therefore increasing your cook time.