Combine the currants, dates, crystallized ginger, rum, and vanilla extract in a small bowl, and let stand 30 minutes, stirring occasionally.
Beat egg whites and egg at medium speed of a mixer until foamy. Gradually add the brown sugar, beating until well-blended. Add the molasses, and beat well.
Combine the flour, ground ginger, and next 7 ingredients (flour through pepper), and stir well. Combine pumpkin, buttermilk, oil, and melted margarine, and stir well. Add the flour mixture to egg mixture alternately with pumpkin mixture, beginning and ending with flour mixture; mix well after each addition. Fold in the rum-dried fruit mixture.
Spoon batter into a 9 1/2-inch quiche dish coated with cooking spray. Bake at 375° for 55 minutes or until a wooden pick inserted in the center comes out clean; let pie cool for 30 minutes on a wire rack. Serve warm with Cider-Lemon Sauce.
Note: Crystallized ginger is available at large supermarkets and specialty food stores, or it can be mail-ordered from Penzey's Ltd., P.O. Box 1448, Waukesha, WI 53187. Phone 414/574-0277.