Place potatoes in a large saucepan, and cover with cold water. Bring to a boil; cover, reduce heat, and simmer 15 minutes or until tender. Drain; wipe pan dry.
Heat 1 teaspoon oil in saucepan over medium- high heat until hot. Add garlic and rosemary; cook 3 minutes, stirring often.
Add drained potatoes, 1 teaspoon oil, halfand- half, salt, and pepper to garlic mixture. Place over low heat, and mash with a potato masher.