Scrub potatoes prick with a fork and bake at 425 for 45 to 60 minutes until soft to the touch
Cut a lengthwise slice from the top of each potato discard skin from each slice Reserving potato shells scoop out the insides and add to potato portions from top slices
Mash potato pulp add diet margarine and enough milk to make a smooth consistency
Stir in mushrooms
Spoon potato mixture into potato shells
Place in baking dish and bake at 425 for 20 to 25 minutes until lightly browned
Sprinkle each potato with one tablespoon shredded Cheddar cheese and bake until cheese melts about 2 to 3 minutes