Sweet Potato Cobbler

In a saucepan, cook sweet potatoes in water until crisp-tender, about 10 minutes. Drain, reserving 1-1/2 cups cooking liquid. Layer potatoes in a greased 13-in. x 9-in. baking dish; add reserved liquid. Combine sugar, flour, cinnamon, nutmeg and salt; sprinkle over potatoes. Dot with butter. , Preheat oven to 400°. For pastry, combine flour and salt; cut in shortening until mixture resembles coarse crumbs. Gradually add water, tossing with a fork until a ball forms. On a floured surface, roll pastry into a 13-in. x 9-in. rectangle. Place over filling; cut slits in top. Brush with butter; sprinkle with sugar. Bake until top is golden brown, 30-35 minutes. Spoon into dishes; if desired, top with whipped cream.