Place approximately 1 ½ inches of water in a saucepan and turn heat to low. Cut off stems of rosemary and add to water. Finely chop rosemary leaves and set aside.

Process onion directly into Culinary Basket. Sprinkle with half of the rosemary.

Process potatoes directly into the basket over potatoes. Sprinkle with remaining rosemary.

Insert basket in pan and cover. Turn heat to medium. When Vapo-Valve­™ clicks steadily, reduce heat to low and cook approximately 10 - 15 minutes, or until potatoes are soft enough to mash.

Transfer potatoes and onions to a large serving bowl and stir to blend. Grate cheese over warm potatoes, if desired, and allow to melt.