Cut a slit in the top of each potato and lightly spray the skin all over with cooking spray. Arrange the potatoes on an ungreased rimmed baking sheet and bake until tender, about 1 hr.
Slice off the top third of each potato. scoop out the insides into a med bowl and mash with the american cheese, yogurt, milk, salt and pepper. Return the potato shells to the baking sheet. scrape the mixture back into the shells. sprinkle with peprika and bake until golden, about 30 min. top with the scallions and serve