Heat oven to 450 degrees F. Scrub potatoes; pat dry. Using fork, pierce each potato in several places. Place on middle rack of oven; bake 45 minutes until centers are tender when pierced with metal skewer. Remove from oven; reduce temperature to 350 degrees F. Cut potatoes lengthwise in half; using teaspoon, carefully scoop potato flesh into medium-size bowl, leaving 1/8-inch layer of flesh attached to skin. Set potato shells aside. With potato masher or heavy fork, mash together potato flesh, cottage cheese, yogurt and dill until well blended. Stir in chopped scallions. Spoon mixture lightly into shells; place in shallow baking dish. Bake 10 to 15 minutes until filling is hot. Sprinkle tops of potatoes with grated Cheddar and sliced scallions. Serve immediately.