Peel the potatoes and boil in water until soft. Mash and let cool. Crush and peel a whole head of garlic. Cut into quarters. Place raw garlic in a heavy duty blender with the salt and lemon juice. Pour a light layer of oil onto garlic. Puree the garlic, salt lemon juice on high and begin pouring a slow steady stream of the rest of the oil through the blender's handle hole until everything has mixed.