In a large bowl, cream butter and sugar until light and fluffy. Beat in the eggs, milk and molasses. Combine the flour, baking powder, baking soda and spices; gradually add to creamed mixture. Stir in the apple, raisins, cherries and dates.
Pour into a well-greased 6-cup pudding mold or metal gelatin mold. Cover with foil. Place on a rack in a deep kettle. Add 1 in. of boiling water to kettle; cover and boil gently for 2 to 2-1/2 hours or until a toothpick inserted near the center comes out clean, replacing water as needed. Let stand for 5 minutes before unmolding.
In a small saucepan, combine sugar and cornstarch. Stir in water until smooth. Bring to a boil over medium heat; cook and stir for 1-2 minutes or until thickened. Remove from the heat. Stir in butter and nutmeg. Unmold pudding onto a serving plate; cut into wedges. Serve warm with sauce. Yield: 8 servings (1/2 cup sauce).