Pierce skin of each potato with a fork, and bake for 1 hour to 1 hour and 15 minutes, until soft. Conversely, microwave at full power in 5 minute increments until soft to the touch. (Probably 15 minutes total.)
Cut each potato in half and scoop out flesh into mixing bowl.
Add salt, garlic powder and heavy cream and mix well, using hand mixer or whipping well by hand. Put potato mixture in sprayed casserole. Potatoes can be held at this point until needed: refrigerate if the potatoes will be held for more than an hour, and allow to come to room temperature before broiling.
Dot top of casserole with butter and sprinkle with paprika.
Heat casserole through at 450 degrees if allowed to come to temp prior, then broil until crispy and browned, about 5 minutes.