Preparation Put oven rack in middle position and preheat oven to 375°F. Butter baking dish. Purée cottage cheese in a food processor until as smooth as possible, about 1 minute, then add butter, 1 teaspoon salt, and 1/2 teaspoon pepper and blend until combined well. Peel potatoes and cut crosswise using slicer into 1/8-inch-thick slices. Spread one third of potatoes evenly in 1 layer in dish and top with one third (a scant cup) cottage cheese mixture (mixture will not cover potatoes completely). Continue layering potatoes and cottage cheese mixture, ending with mixture. Cover tightly with foil and bake until potatoes are tender, 1 to 1 1/4 hours. Whisk together eggs, yogurt, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon pepper in a bowl. Pour egg mixture evenly over potatoes and bake, uncovered, until custard is set, about 20 minutes. Cooks' note:Potatoes with custard can be baked 1 day ahead and cooled completely, then chilled, covered with foil. Reheat, covered, in a 375°F oven until hot, about 30 minutes.
Preparation Put oven rack in middle position and preheat oven to 375°F. Butter baking dish. Purée cottage cheese in a food processor until as smooth as possible, about 1 minute, then add butter, 1 teaspoon salt, and 1/2 teaspoon pepper and blend until combined well. Peel potatoes and cut crosswise using slicer into 1/8-inch-thick slices. Spread one third of potatoes evenly in 1 layer in dish and top with one third (a scant cup) cottage cheese mixture (mixture will not cover potatoes completely). Continue layering potatoes and cottage cheese mixture, ending with mixture. Cover tightly with foil and bake until potatoes are tender, 1 to 1 1/4 hours. Whisk together eggs, yogurt, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon pepper in a bowl. Pour egg mixture evenly over potatoes and bake, uncovered, until custard is set, about 20 minutes. Cooks' note:Potatoes with custard can be baked 1 day ahead and cooled completely, then chilled, covered with foil. Reheat, covered, in a 375°F oven until hot, about 30 minutes.