Preheat oven to 400 degrees. Puncture potatoes with a fork about 6 times around the potato, this will allow steam to escape while they are cooking. Bake for 50-60 minutes or until the skins are crispy but the potato is soft. You should be able to insert a fork and remove it easily. Reduce oven temperature to 350 degrees.

Slice the potatoes in half lengthwise (Note: be careful they will retain a lot of the heat for awhile). Being careful not to puncture the skin, spoon out the insides, place them in a mixing bowl and set the skins aside.

To potatoes ad butter and milk. Mash. Then fold in 1/2 cup of mozzarella cheese and rosemary. Carefully spoon mash back into potato skins. Top with remaining mozzarella. Bake in preheated oven for 25 minutes or until cheese is melted. Turn on the broiler and broil for 2 - 3 minutes or until the cheese on top starts to brown. Serve immediately