Bake potatoes in preheated 425-degree oven until soft, about 60 minutes
While potatoes are baking, cut skin from squash. Cut squash into small cubes and place in vegetable steamer, covered, over boiling water for 15 minutes or until very soft.
Cool potatoes slightly. Cut them in half while still warm and gently scrape pulp from skin, taking care not to tear skin.
Combine squash, potato pulp, 1/4 cup melted butter, cumin, and sea salt with potato masher until you have a creamy yellow puree.
Heap potato-squash mixture into empty potato shells. Brush with 2 teaspoons melted better and sprinkle with paprika.
Place under broiler for 10 minutes or until lightly browned.