In a small bowl combine sugar and cinnamon; set aside 1 teaspoon of the mixture. Stir the cornstarch and salt into the remaining sugar mixture; sprinkle evenly over the apples in the baking dish.
In a medium bowl stir together the flour and nutmeg. Using a pastry blender, cut in butter until pieces are pea-size. Sprinkle 1 tablespoon of the water over part of the flour mixture; gently toss with a fork. Push moistened dough to side of bowl. Repeat, using 1 tablespoon at a time, until all the flour mixture is moistened. Form into a ball.
On a lightly floured surface, slightly flatten dough. Roll dough from center to edges into a 10-inch square. Cut decorative vents in pastry. Carefully place pastry over apples. Using the tines of a fork, press edges to sides of dish. Brush pastry with milk and sprinkle with the reserved sugar mixture.
Bake in a 375 degree F oven about 40 minutes or until the apples are tender and the crust is golden. Serve warm. If desired, serve with frozen yogurt. Makes 8 servings.