Peel potatoes and cut in half. Place in large stovetop pot with 4 whole garlic cloves. Cover with cold water and bring to a boil. Reduce heat to a gentle boil and cook until potatoes are tender.
When potatoes are tender, drain and mash along with garlic cloves using a potato masher or electric beaters.
Stir butter or olive oil, sage, salt, pepper and sour cream or buttermilk into the remaining potatoes and return to low heat, stirring until warm.