Pierce each potato with a fork 3 to 4 times on each side. Wrap each potato in a damp paper towel. Microwave at HIGH 8 minutes, turning after 4 minutes. Cool slightly. Cut potatoes in half; scoop pulp into a bowl. Mash pulp.
Stir butter, milk, sage, Parmesan cheese, and salt into potato pulp.
These turned out really delicious. Very creamy. The Parmesan and sage combination gave it a new flavor twist. There were about five mashed sweet potato dishes at our Thanksgiving and everyone praised this recipe as the best!!