Fill a pot with 1-2 inches of water then place a steamer basket in it. Place the pot on the stove and turn the heat on to medium-high.
Wash and scrub the potatoes well, then peel and cut them into medium sized pieces.
Place the potatoes in the steamer basket and cover the pot. Steam for about 10 minutes, or until the potatoes are soft.
Let the potatoes cool slightly. Then, add them to a blender along with the rosemary and a splash of liquid to get the blender started. Puree the potatoes, adding more liquid as necessary. Turn the blender off a soon as the puree is smooth (over blending the potatoes can cause them to become very “gummy.”
Mix the potato puree with more liquid as needed, until you reach your desired consistency.