Begin by peeling and dicing the potatoes, then reserve them in cold water. Transfer the water and potatoes into a medium sized pot. Cook over high heat and bring to a boil, lower the heat and cook for an additional 8 to 10 minutes. When they are fork tender, transfer the potatoes to a strainer and drain. Return potatoes to pot. In a small pan, heat the butter, cream and garlic. Add the butter/cream mixture to the potatoes and mash with wooden spoon or masher. Be careful not to over whip. Finally add the rosemary, salt, and freshly ground black pepper, to taste.